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The ultra-wide bandgap of gallium oxide provides a rich plethora of electrically active defects. Understanding and controlling such defects is of crucial importance in mature device processing. Deep-level transient spectroscopy is one of the most sensitive techniques for measuring electrically active defects in semiconductors and, hence, a key technique for progress toward gallium oxide-based components, including Schottky barrier diodes and field-effect transistors. However, deep-level transient spectroscopy does not provide chemical or configurational information about the defect signature and must, therefore, be combined with other experimental techniques or theoretical modeling to gain a deeper understanding of the defect physics. Here, we discuss the current status regarding the identification of electrically active defects in beta-phase gallium oxide, as observed by deep-level transient spectroscopy and supported by first-principles defect calculations based on the density functional theory. We also discuss the coordinated use of the experiment and theory as a powerful approach for studying electrically active defects and highlight some of the interesting but challenging issues related to the characterization and control of defects in this fascinating material. [ABSTRACT FROM AUTHOR]

Irradiation of semiconductors by energetic beams generates excess electrons and holes and may cause device degradation or failure. Both gradual degradation by total ionizing radiation (TID) and sudden degradation/failure (soft/hard breakdown) by a combination of energetic heavy ions and high voltages (typically single-event effects or SEEs) are mediated by excess carriers. The role of defect dynamics in TID degradation has been adequately understood by a combination of experiments and density-functional-theory (DFT) quantum calculations, but little has been done so far to document a role for ion-induced defects in SEE. Here, we report proof-of-principle DFT calculations in a model cubic GaN system for two defect-related excess-carrier phenomena that can play a role in various forms of device degradation and failure. The first phenomenon is the existence, dynamics, and potential roles of defect-induced quasi-localized "resonant states" in the energy-band continua. These states can enhance TID-excess-carrier and hot-carrier degradation. Furthermore, they evolve and multiply during energetic-ion-induced atom recoils and defect creation (displacement damage) and can potentially serve as excess-carrier conduction paths in SEE. The second phenomenon is the conversion of isolated vacancies into nanovoids that can participate in the formation of conducting defect "nanowires" dressed by resonances or in explosive SEE hard breakdowns. [ABSTRACT FROM AUTHOR]

Since the 1940s, it has been known that diffusion in crystalline solids occurs due to lattice defects. The diffusion of defects can have a great impact on the processing and heat treatment of materials as the microstructural changes caused by diffusion can influence the material qualities and properties. It is, therefore, vital to be able to control the diffusion. This implies that we need a deep understanding of the interactions between impurities, matrix atoms, and intrinsic defects. The role of density functional theory (DFT) calculations in solid-state diffusion studies has become considerable. The main parameters to obtain in defect diffusion studies with DFT are formation energies, binding energies, and migration barriers. In particular, the utilization of the nudged elastic band and the dimer methods has improved the accuracy of these parameters. In systematic diffusion studies, the combination of experimentally obtained results and theoretical predictions can reveal information about the atomic diffusion processes. The combination of the theoretical predictions and the experimental results gives a unique opportunity to compare parameters found from the different methods and gain knowledge about atomic migration. In this Perspective paper, we present case studies on defect diffusion in wide bandgap semiconductors. The case studies cover examples from the three diffusion models: free diffusion, trap-limited diffusion, and reaction diffusion. We focus on the role of DFT in these studies combined with results obtained with the experimental techniques secondary ion mass spectrometry and deep-level transient spectroscopy combined with diffusion simulations. [ABSTRACT FROM AUTHOR]

The concentration of vacancies and impurities in semiconductors plays a crucial role in determining their electrical, optical, and thermal properties. This study aims to clarify the nature of the interaction between positrons and ionized p-type impurities, emphasizing the similarities they share with the interaction between holes and this type of impurity. An overall strategy for investigating defects in semiconductor crystals that exhibit a combination of vacancies and p-type impurities is presented. By using positron annihilation spectroscopy, in particular, Doppler broadening of the annihilation radiation, we quantify the concentration of vacancies in epitaxial Si crystals grown by low-energy plasma-enhanced chemical vapor deposition. The vacancy number densities that we find are (1.2 ± 1.0) × 1017 cm−3 and (3.2 ± 1.5) × 1020 cm−3 for growth rates of 0.27 and 4.9 nm/s, respectively. Subsequent extended annealing of the Si samples effectively reduces the vacancy density below the sensitivity threshold of the positron technique. Secondary ion mass spectrometry indicates that the boron doping remains unaffected during the annealing treatment intended for vacancy removal. This study provides valuable insights into the intricate interplay between vacancies and ionized impurities with positrons in semiconductor crystals. The obtained results contribute to advance the control and understanding of material properties in heterostructures by emphasizing the significance of managing vacancy and dopant concentrations. [ABSTRACT FROM AUTHOR]

Electronic relaxation dynamics of solution-phase redox-exfoliated molybdenum disulfide (MoS2) monolayer and multilayer ensembles are described. MoS2 was exfoliated using polyoxometalate (POM) reductants. This process yields a colloidal heterostructure consisting of MoS2 2D sheet multilayers with surface-bound POM complexes. Using two-dimensional electronic spectroscopy, transient bleaching and photoinduced absorption signals were detected at excitation/detection energies of 1.82/1.87 and 1.82/1.80 eV, respectively. Approximate 100-fs bandgap renormalization (BGR) and subsequent defect- and phonon-mediated relaxation on the picosecond timescale were resolved for several MoS2 thicknesses spanning from 1 to 2 L to ∼20 L. BGR rates were independent of sample thickness and slightly slower than observations for chemical vapor deposition-grown MoS2 monolayers. However, defect-mediated relaxation accelerated ∼10-fold with increased sample thicknesses. The relaxation rates increased from 0.33 ± 0.05 to 1.2 ± 0.1 and 3.1 ± 0.4 ps−1 for 1–2 L, 3–4 L, and 20 L fractions. The thicknesses-dependent relaxation rates for POM-MoS2 heterostructures were modeled using a saturating exponential function that showed saturation at thirteen MoS2 layers. The results suggest that the increased POM surface coverage leads to larger defect density in the POM-MoS2 heterostructure. These are the first descriptions of the influence of sample thickness on electronic relaxation rates in solution-phase redox-exfoliated POM-MoS2 heterostructures. Outcomes of this work are expected to impact the development of solution-phase exfoliation of 2D metal-chalcogenide heterostructures. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold immense promise as ultrathin-body semiconductors for cutting-edge electronics and optoelectronics. In particular, their sustained charge mobility even at atomic-level thickness as well as their absence of surface dangling bonds, versatile band structures, and silicon-compatibility integration make them a prime candidate for device applications in both academic and industrial domains. Despite such high expectations, group-VI TMDs reportedly exhibit a range of enigmatic properties, such as substantial contact resistance, Fermi level pinning, and limited unipolar charge transport, which are all rooted in their inherent defects. In other words, intrinsic physical properties resulting from their native defects extend their influence beyond the material level. Bridging point-defect-induced material properties and their behavior at the device level, this Perspective sheds light on the significance of crystalline defects beyond a rather simple defect–property relationship. As a distinctive approach, we briefly review the well-established defect model of conventional III–V semiconductors and further apply it to the emergent defect behaviors of 2D TMDs such as their defect-induced gap states. Within the main discussion, we survey a range of behaviors caused by the most prevalent intrinsic defect, namely, vacancies, within 2D TMDs, and their implications for electronic and optoelectronic properties when employed at the device level. This review presents an in-depth summary of complexities in material properties as well as device characteristics arising from intrinsic point defects and provides a solid foundation for the cross-links among native defects and material/device properties. [ABSTRACT FROM AUTHOR]

This Perspective focuses on experimental and theoretical aspects of positron annihilation spectroscopy. This set of methods is highly suitable for identifying and quantifying vacancy-type defects in semiconductors and also allows for analyzing their physics characteristics. We present selected examples from the past decade, where the methods have been used for obtaining timely and useful insights into the defect-controlled phenomenon in narrow-gap (Ge, GaSb) and wide-gap (III-nitride, oxide) semiconductors. We also discuss possible future developments that may allow more detailed studies in novel semiconductor materials and devices with ever more complex lattice structures. [ABSTRACT FROM AUTHOR]

Radiation damage in semiconductor materials is a crucial concern for electronic applications, especially in the fields of space, military, nuclear, and medical electronics. With the advancements in semiconductor fabrication techniques and the trend of miniaturization, the quality of semiconductor materials and their susceptibility to radiation-induced defects have become more important than ever. In this context, machine learning (ML) algorithms have emerged as a promising tool to study minor radiation-induced defects in semiconductor materials. In this study, we propose a sensitive non-destructive technique for investigating radiation-induced defects using multivariate statistical analyses combined with Raman spectroscopy. Raman spectroscopy is a contactless and non-destructive method widely used to characterize semiconductor materials and their defects. The multivariate statistical methods applied in analyzing the Raman spectra provide high sensitivity in detecting minor radiation-induced defects. The proposed technique was demonstrated by categorizing 100–500 kGy irradiated GaAs wafers into samples with low and high irradiation levels using linear discrimination analysis ML algorithms. Despite the high similarity in the obtained Raman spectra, the ML algorithms correctly predicted the blind testing samples, highlighting the effectiveness of ML in defect study. This study provides a promising approach for detecting minor radiation-induced defects in semiconductor materials and can be extended to other semiconductor materials and devices. [ABSTRACT FROM AUTHOR]

Halide perovskites are essential materials for hard radiation detectors at ambient temperature. To improve detector performance, charge transport must be investigated and optimized. Using photoluminescence (PL) and thermally stimulated current (TSC) spectroscopies, we investigate photogenerated charge carriers in Bridgman-grown CsPbBr3 single crystals to understand the nature of charge transport. PL spectroscopy of these halide perovskites revealed the presence of strong emission bands at the band edge, which were attributed to free or bound excitons. It is shown that a wide broadening of the excitonic linewidth in these halide perovskites arises from strong exciton–phonon coupling, which is substantially dominated by longitudinal optical phonons via Fröhlich interaction. An additional contribution due to the presence of ionized impurities was also observed. Crystals with a detectable sensitivity to high-energy gamma radiation are characterized by a higher intensity and a narrower linewidth of the principal PL peak at 2.326 eV. Defect states beyond 2.214 eV have a negative impact on detector sensitivity to high-energy gamma radiation. TSC spectroscopy reveals an array of trap levels spanning 0.15–0.70 eV, attributed to intrinsic point defects and multiple extrinsic defects involving dopants or impurities. Defects identified included Cs and Br vacancies, as well as Pb interstitials with concentrations in the 1011–1016 cm−3 range. Understanding how the synthesis process impacts the types and concentrations of the defects present is currently under investigation. Elimination or suppression of the defect/trap states should result in halide perovskite materials with longer carrier diffusion lengths and improved detector characteristics. [ABSTRACT FROM AUTHOR]

Harnessing the boundless solar energy, photovoltaic cells emerge as pivotal players in the world's sustainable energy landscape. The efficiency of solar cells is intimately tied to the carrier properties influenced by defects and impurities within the sunlight-absorbing semiconductors. In this Perspective, we offer a brief overview of recent advances in exploring doping properties with a focus on three vital thin-film photovoltaic semiconductors: CdTe, CIGS, and halide perovskites. Our discourse encompasses their electronic band structure, intrinsic and extrinsic doping behaviors, defect-assisted nonradiative recombination losses, as well as promising strategies poised to enhance solar cell efficiency. Additionally, we discuss several lingering challenges associated with defects in the advancement of photovoltaic technologies. [ABSTRACT FROM AUTHOR]

Magnetic semiconducting materials offer tremendous prospects for spin electronics but is challenging to achieve room-temperature ferromagnetism with unambiguous origin. Herein, a non-stoichiometry strategy is proposed to induce tunable magnetization in MoSe2−x nanoflowers via vacancy-controlled 2H–1T phase transition. The resultant MoSe2−x exhibits robust room-temperature ferromagnetism with significant positive correlation to the content of 1T phase and 2H–1T interfaces. Significant magnetic hysteresis and Curie transition above room temperature have been achieved, confirming the ferromagnetic feature of MoSe2−x. To examine the origin of ferromagnetism, formation energy and spin-polarized calculations have been conducted, indicating that the Se vacancy is beneficial for the formation of the 1T phase and interfacial spin polarization. Localized magnetic moments induced at the 2H–1T interfaces exhibit enhanced magnetism as compared to the net moments from the 1T orbital splitting, giving rise to strong coupling bound magnetic polarons. This work not only advances the understanding on the origin of magnetism in magnetic semiconductors, but also provides an effective route to generate ferromagnetism by defect and/or interface engineering that could be applied to multiferroics, spintronics, and valleytronics. [ABSTRACT FROM AUTHOR]

Transition state calculation is a critical technique to understand and predict versatile dynamical phenomena in solids. However, the transition state results obtained at 0 K are often utilized for the prediction or interpretation of dynamical processes at high temperatures, and the error bars of such an approximation are largely unknown. In this benchmark study, all the major temperature effects, including lattice expansion, lattice vibration, electron excitation, and band-edge shift, are evaluated with first-principles calculations for defect diffusion in solids. With the inclusion of these temperature effects, the notable discrepancies between theoretical predictions at 0 K and the experimental diffusivities at high temperatures are dramatically reduced. In particular, we find that lattice expansion and lattice vibration are the dominant factors lowering the defect formation energies and hopping barriers at high temperatures, but the electron excitation exhibits minor effects. In sharp contrast to typical assumptions, the attempt frequency with lattice expansion and vibration varies significantly with materials: several THz for aluminum bulk but surprisingly over 500 THz for 4H-SiC. For defects in semiconductors, the band-edge shift is also significant at high temperatures and plays a vital role in defect diffusion. We expect that this study would help accurately predict the dynamical processes at high temperatures. [ABSTRACT FROM AUTHOR]

Optically active spin defects in semiconductors can serve as spin-to-photon interfaces, key components in quantum technologies. Silicon carbide (SiC) is a promising host of spin defects thanks to its wide bandgap and well-established crystal growth and device technologies. In this study, we investigated the oxygen-vacancy complexes as potential spin defects in SiC by means of ab initio calculations. We found that the OCVSi defect has a substantially low formation energy compared with its counterpart, OSiVC, regardless of the Fermi level position. The OCVSi defect is stable in its neutral charge state with a high-spin ground state (S = 1) within a wide energy range near the midgap energy. The zero-phonon line (ZPL) of the OCVSi0 defect lies in the near-infrared regime, 1.11–1.24 eV (1004–1117 nm). The radiative lifetime for the ZPL transition of the defect in kk configuration is fairly short (12.5 ns). Furthermore, the estimated Debye–Waller factor for the optical transition is 13.4%, indicating a large weight of ZPL in the photoluminescence spectrum. All together, we conclude that the OCVSi0 defect possesses desirable spin and optical properties and thus is potentially attractive as a quantum bit. [ABSTRACT FROM AUTHOR]

An innovative approach is proposed to passivate the existing defects from metal oxide semiconductors by functionalizing nontoxic bio-based substances. As a demonstration, we synthesized zinc oxide nanorods (ZnO NRs) using a hydrothermal method and incorporated chicken egg white (albumen) as a passivator to the defects. X-ray diffraction analysis of ZnO NRs shows enhanced quality and crystallinity features after incorporating albumen. XPS measurements were performed not only to introduce the chemical bonding between the albumen and the bare ZnO NRs but also specifically provide evidence of successful capping and defect passivation to the surface layer of ZnO NRs. It was observed that when the albumen was annealed, it formed sulfhydryl groups and disulfide bonds (which created disulfide bridges) from the chemical reaction in irreversible thermal denaturation. Steady-state photoluminescence of ZnO NRs showed two emission bands, i.e. near band-edge emission (NBE) and deep-level emission (DL). The NBE is significantly improved as compared to DL emission after capping and annealing the albumen, while the quenching of DL emission confirmed the reduced defects arising from the surface of ZnO NRs. The advantages and enhanced characteristics of the albumen-capped ZnO NRs led to fabricating a stable and highly efficient light-emitting device. This work opens the great potential of utilizing nontoxic and low-cost biomaterials in passivating the defects of metal oxide nanomaterials for the development of bio-inspired and stable optoelectronic devices. [ABSTRACT FROM AUTHOR]

The introduction of oxygen defects in semiconductor electronic structures is considered to be an effective strategy to improve their photocatalytic activity. In this work, rare-earth Er3+−doped BiOBr (Er/BiOBr) with oxygen-rich vacancies (OVs) was prepared via simple hydrothermal method. Compared with pure BiOBr, Er/BiOBr has a narrower band gap and more abundant OVs, which together improve the separation efficiency of photogenerated carriers. The introduction of Er not only creates impurity states between conduction band (CB) and valence band (VB), but also produces more OVs as electron traps. Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used as evaluation systems for these materials with different Er3+ doping contents. The results showed that under the combined action of ·O 2 − and H 2 O 2 , 2.0% EBB samples with Er3+ doping content of BiOBr showed the best broad-spectrum antibacterial activity, and E. coli and S. aureus were completely inactivated at 0.03 mg ml−1 and 0.05 mg ml−1 concentrations. The surface and interfacial structures of Er/BiOBr samples were studied by XRD, brunauer-emmet-teller method, SEM, TEM and EDX. OVs and photogenerated carrier separation in Er/BiOBr were determined by ESR, PL and photochemical detection methods. More importantly, through the detection of lipid peroxidation and bacterial respiratory chain dehydrogenase activities, the internal and external processes of ROS on bacterial inactivation were determined, and the photocatalytic antibacterial mechanism was summarized. This study for the antimicrobial properties of rare earth ions doped improve photocatalytic materials provides a new train of thought. [ABSTRACT FROM AUTHOR]

Constructive defect engineering has emerged as a prominent method for enhancing the performance of photocatalysts. The mechanisms of the influence of defect types, concentrations, and distributions on the efficiency, selectivity, and stability of CO2 reduction were revealed for this paper by analyzing the effects of different types of defects (e.g., metallic defects, non-metallic defects, and composite defects) on the performance of photocatalysts. There are three fundamental steps in defect engineering techniques to promote photocatalysis, namely, light absorption, charge transfer and separation, and surface-catalyzed reactions. Defect engineering has demonstrated significant potential in recent studies, particularly in enhancing the light-harvesting, charge separation, and adsorption properties of semiconductor photocatalysts for reducing processes like carbon dioxide reduction. Furthermore, this paper discusses the optimization method used in defect modulation strategy to offer theoretical guidance and an experimental foundation for designing and preparing efficient and stable photocatalysts. [ABSTRACT FROM AUTHOR]

The optical absorption coefficient is one of the fundamental properties of semiconductors and is critical to the development of optical devices. Herein, a revival of the constant photocurrent method is presented to measure sub‐bandgap absorption in wide bandgap semiconductor films. The method involves maintaining a constant photocurrent by continually adjusting the impinging photon flux across the energy spectrum. Under such conditions, the reciprocal of the photon flux for uniformly absorbed light is proportional to the absorption coefficient. This method is applied to α‐Ga2O3 and reveals that it can access the absorption coefficient from 1 × 105 cm−1 at the band edge (5.3 eV) to 0.8 cm−1 close to mid‐bandgap (2.7 eV). Changes in the steepness of the absorption curve in the sub‐bandgap region are in excellent agreement with defect states of α‐Ga2O3 reported by deep level transient spectroscopy, indicating that the technique shows promise as a probe of energetically distributed defect states in thin film wide bandgap semiconductors. [ABSTRACT FROM AUTHOR]

As a rediscovered ternary two-dimensional (2D) material, defect-rich Znln2S4 has great potential for energy-harvesting applications. However, the effect of defects on its physical properties and device performance remains elusive. Herein, we explored the influence of defects (S vacancies and In–Zn substitutions) in few-layer Znln2S4 on the charge transport and photoelectric performance. It is demonstrated that the defect-rich Znln2S4 device exhibits two-dimensional variable range hopping transport mechanism, with uniform charge transport along the channel and low contact resistance at the electrical contacts of Znln2S4/Au. Importantly, due to the contribution of the donor and acceptor energy levels inside the bandgap, the flake exhibits pronounced extrinsic absorption, leading to the competitive photodetector performance under sub-bandgap photo-excitation. Explicitly, the device exhibits a maximum responsivity of 4.08 × 104 A W−1, a photo-gain of >108 electrons per photon, and a specific detectivity of ∼1015 Jones under 532 nm laser excitation, with detection wavelength extending from 400 to 980 nm. Our findings underscore the significant potential of defect-engineering to enrich the functionalities of 2D semiconductors. [ABSTRACT FROM AUTHOR]

Heterojunctions have been recognized as promising candidates for the fabrication of broadband photodetectors. However, currently demonstrated heterojunctions suffer from one or more disadvantages in limited light absorption, incompatible fabrication with the current semiconductor technology, and/or abundant interface defects induced by lattice/thermal mismatches. In this work, we use traditional elemental semiconducting materials to construct n+-Si/p-Ge heterojunctions by the transfer printing method, which are further explored as broadband photodetectors. Key advantages are in capabilities for avoiding the defects induced by the lattice and thermal expansion mismatches, and for detecting the illuminated light with the wavelength covering the visible-near-infrared range. Controlling the layer stacking order of the heterojunction could enable a complementary optoelectronic interaction between Si and Ge, which facilitates the effective generation of electron–hole pairs in a wide spectrum of light illumination. This work adds to the portfolio of material strategies and fabrication approaches in high-performance broadband photodetectors. [ABSTRACT FROM AUTHOR]

Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface‐to‐volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade‐off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n‐type single crystal. Step edges, serving as adsorption sites with electron‐deficient properties, are well‐defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap‐like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two‐terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi‐log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing. [ABSTRACT FROM AUTHOR]

Use and performance criteria of photonic devices increase in various application areas such as information and communication, lighting, and photovoltaics. In many current and future photonic devices, surfaces of a semiconductor crystal are a weak part causing significant photo-electric losses and malfunctions in applications. These surface challenges, many of which arise from material defects at semiconductor surfaces, include signal attenuation in waveguides, light absorption in light emitting diodes, non-radiative recombination of carriers in solar cells, leakage (dark) current of photodiodes, and light reflection at solar cell interfaces for instance. To reduce harmful surface effects, the optical and electrical passivation of devices has been developed for several decades, especially with the methods of semiconductor technology. Because atomic scale control and knowledge of surface-related phenomena have become relevant to increase the performance of different devices, it might be useful to enhance the bridging of surface physics to photonics. Toward that target, we review some evolving research subjects with open questions and possible solutions, which hopefully provide example connecting points between photonic device passivation and surface physics. One question is related to the properties of the wet chemically cleaned semiconductor surfaces which are typically utilized in device manufacturing processes, but which appear to be different from crystalline surfaces studied in ultrahigh vacuum by physicists. In devices, a defective semiconductor surface often lies at an embedded interface formed by a thin metal or insulator film grown on the semiconductor crystal, which makes the measurements of its atomic and electronic structures difficult. To understand these interface properties, it is essential to combine quantum mechanical simulation methods. This review also covers metal-semiconductor interfaces which are included in most photonic devices to transmit electric carriers to the semiconductor structure. Low-resistive and passivated contacts with an ultrathin tunneling barrier are an emergent solution to control electrical losses in photonic devices. [ABSTRACT FROM AUTHOR]

The semiconductor minority carrier lifetime contains information about several important material properties, including Shockley–Read–Hall defect levels/concentrations and radiative/Auger recombination rates, and the complex relationships between these parameters produce a non-trivial temperature-dependence of the measured lifetime. It is tempting to fit temperature-dependent lifetime data to extract the properties of the Shockley–Read–Hall recombination centers; however, without a priori knowledge of the distribution of the Shockley–Read–Hall states across the bandgap, this fit problem is under-constrained in most circumstances. Shockley–Read–Hall lifetime data are not well-suited for the extraction of Shockley–Read–Hall defect levels but can be used effectively to extract minority carrier recombination lifetimes. The minority carrier recombination lifetime is observed at temperatures below 100 K in a Si-doped n-type InGaAs/InAsSb superlattice, and deviation from its expected temperature-dependence indicates that the capture cross section of the defect associated with Si-doping has an activation energy of 1.5 meV or a characteristic temperature of 17 K. This lower temperature regime is also preferrable for the analysis of the physics of defect introduction with displacement-damage-generating particle irradiation. [ABSTRACT FROM AUTHOR]

In this paper, an attempt has been made to investigate a one-dimensional photonic crystal containing N-doped germanium semiconductor as a nonlinear defect layer with an intensity-dependent refractive index, silica (SiO2) and zinc selenide (ZnSe) as crystal cells. Bistability of the TE polarization of the transmission spectrum due to the nonlinear property of the defect layer is investigated by the transfer matrix method (TMM). The refractive index of the germanium nonlinear semiconductor layer is simultaneously depending on the doping density and the intensity of the irradiated light. The changes in both factors are investigated. The impact on the transmission spectrum of the bistability threshold due to the change in the thickness of the defect layer, the thickness of other layers of crystal cells, and the angle of incident light are investigated. The nonlinear effect caused by light intensity as well as doped density effect on the germanium nonlinear semiconductor medium is used simultaneously. As a result, the nonlinear effect caused by the light intensity to create bistability is more than the doping density. [ABSTRACT FROM AUTHOR]

Vertical semiconductor van der Waals heterojunctions are essential for fabricating high-performance photodetectors. However, the range of the spectral response and defect states of semiconductor materials are two critical factors affecting the performance of photodetectors. In this work, the spectral response range of WS2 was changed through WS2 band gap regulation, and a self-powered vertical WS1.08Se0.92/Si heterojunction photodetector with MXene electrode was prepared by synthesizing WS1.08Se0.92 film on Si substrate and vertically stacking Ti3C2T x MXene on the film. Due to the electron collection of MXene and the wonderful junction quality of WS1.08Se0.92/Si, the photodetector can detect near-infrared light in the range of 980–1310 nm, which exceed the detection limit of WS1.08Se0.92. And the device had high sensitivity in the broadband. The responsivity was 4.58 A W−1, the specific detectivity was 4.58 × 1011 Jones, the on/off ratio was 4.95 × 103, and the fast response time was 9.81/9.03 μ s. These properties are superior to previously reported WS2-based photodetectors. Vertical structure, Energy band tuning, and MXene electrode provide a new idea for preparing broadband high-performance and self-powered photodetector. [ABSTRACT FROM AUTHOR]

Thus, defects in semiconductors remain a vibrant field of research, as highlighted by the increasing attendance of the relevant international conferences, such as the International Conference on Defects in Semiconductors.[1] The research field of defects in semiconductors encompasses a wide range of topics, combining theoretical modeling and experimental investigations. Understanding defects has been a continuous endeavor in traditional semiconductors, such as silicon (Si) and gallium arsenide, and is critical in the development of new semiconductors and components. SUMMARY OF AREAS COVERED A. Defects in group IV semiconductors Semiconductors from group IV of the periodic table, such as Si and SiC, are mature materials with decades of development, including defect studies. Defects create key functionalities in semiconductor devices by contributing with charge carriers or assisting optical transitions. [Extracted from the article]

Bi2O2Se, a newly emerging two-dimensional (2D) material, has attracted significant attention as a promising candidate for optoelectronics applications due to its exceptional air stability and high mobility. Generally, mica and SrTiO3 substrates with lattice matching are commonly used for the growth of high-quality 2D Bi2O2Se. Although 2D Bi2O2Se grown on these insulating substrates can be transferred onto Si substrate to ensure compatibility with silicon-based semiconductor processes, this inevitably introduces defects and surface states that significantly compromise the performance of optoelectronic devices. Herein we employ Bi2Se3 as the evaporation source and oxygen reaction to directly grow Bi2O2Se nanosheets on Si substrate through a conventional chemical vapor deposition method. The photodetector based on the Bi2O2Se nanosheets on Si substrate demonstrates outstanding optoelectronics performance with a responsivity of 379 A W−1, detectivity of 2.9 × 1010 Jones, and rapid response time of 0.28 ms, respectively, with 532 nm illumination. Moreover, it also exhibits a broadband photodetection capability across the visible to near-infrared range (532–1300 nm). These results suggest that the promising potential of Bi2O2Se nanosheets for high-performance and broadband photodetector applications. [ABSTRACT FROM AUTHOR]

Hydrogen is becoming more widely accepted as a potential energy carrier due to zero emissions, superior energy capacity, and ecological sustainability. It can be produced in a number of ways, but photocatalytic water splitting using sunlight has recently attracted attention as a sustainable option. Photocatalysts based on semiconductors, especially TiO 2 photocatalysts, have been the subject of extensive study because of their desirable physicochemical properties. There are still obstacles to overcome, however, including a wide bandgap, sluggish electron-hole recombination, and the potential for excessive H 2 generation. Numerous strategies such as doping, defect engineering, dye sensitization, and semiconductor coupling have been investigated with the goal of improving the performance of TiO 2 by discovering solutions to these limitations. This article summarizes current research on the multiple parameters affecting the photocatalytic process in dynamic H 2 generation. Surface area, particle size, TiO 2 loading, pH, temperature, light source, light intensity, sacrificial reagents, and band gap energy are all important characteristics of photocatalysts. The techno-feasible analysis, current challenges, possibility for subsequent research, and the potential for H 2 production by the photocatalytic water-splitting process are further addressed in this article. [Display omitted] • Recent attempts involving TiO 2 -based photocatalysts to produce H 2 via photocatalytic water-splitting have been addressed. • Various strategies to improve TiO 2 photocatalytic efficiency have been proposed for practical applications. • Factors affecting the TiO 2 -based photocatalytic efficiency were reviewed. • Techno feasibility analysis water-splitting have been addressed for commercialization. • Several challenges, future perspectives and strategies for development have been proposed. [ABSTRACT FROM AUTHOR]

With the rapid development of intelligent manufacturing and electronic information technology, integrated circuits play a vital role in high-end chips. The semiconductor chip manufacturing process requires precise operation and strict control to ensure chip quality. The traditional manual visual inspection method has a high workforce cost and intense subjectivity and is accompanied by a high level of misdetection and leakage. Computer vision-based wafer defect detection technology is gaining popularity in the industry. However, previous methods still find it challenging to meet the production requirements regarding accuracy. To solve the problem, we propose a defect detection network based on a coding and decoding structure, Dense Skip-Connection U-Net (DSCU-Net), which optimizes the skip connection between the encoder and decoder and enhances the profound fusion of high-level semantics and low-level semantics to improve accuracy. To verify the effectiveness of DSCU-Net, we validate it in actual microelectromechanical systems (MEMS) data, and the results show that DSCU-Net reaches an optimal level. Therefore, the DSCU-Net proposed in this paper effectively solves the defect detection problem in semiconductor chip manufacturing. This method reduces workforce cost and subjectivity interference and improves inspection efficiency and accuracy. It will help to promote further development in the field of intelligent manufacturing and electronic information technology. [ABSTRACT FROM AUTHOR]

Among the renewable energy technologies to deal with increasing energy crisis and environmental concerns, solar-to-chemical conversion via photocatalysis holds great promise for sustainable energy supply. To date, a variety of modification strategies with different types of semiconducting materials have been proposed to boost photocatalytic efficiency. Recently, dual-defect semiconductor photocatalysts have emerged as an advantageous candidate with superior performance in improving photocatalytic activity compared to their defect-free or single-defect counterparts. In this review, focus is laid on the advances of dual-defect semiconductor photocatalysts for energy photocatalysis. Possible schemes for two different defects within a single semiconductor are firstly sorted based on the types of defects, and synthesis strategies to achieve various defect schemes as well as techniques to characterize different defects are then introduced. In particular, the effect of different defects on photocatalytic performance is emphasized, and the advances in dual-defect semiconductors for solar-to-chemical conversions are summarized based on different defect schemes. Finally, the future challenges and opportunities of dual-defect semiconductors for photocatalysis are discussed. This article is expected to provide an overall insight into existing dual-defect semiconductor photocatalysts and inspire the development of new defect-rich materials for photocatalytic energy production. [ABSTRACT FROM AUTHOR]

This study's methodology employs the pristine Armchair Boron Nitride Nanoribbons (ABNNR) and Armchair Boron Nitride Nanoribbons Stone–Wales (ABNNR-SW) defects as carriers for the fluorouracil (FU), Nitrosourea (NU), and Thiotepa (TP) anticancer medicines. Utilizing density functional theory (DFT), the electrical properties of the interaction of FU, NU, and TP anticancer drugs with ABNNR and ABNNR-SW defects were studied. Our results show that ABNNR exhibits isolator behavior with a 6.155 eV energy gap, while the ABNNR-SW defect exhibits semiconductor behavior with a 3.862 eV energy gap. In addition, the energy gap was significantly reduced after the interaction of medicinal molecules with ABNNR and the ABNNR-SW defect substrate. The non-covalent interactions between the ABNNR and ABNNR-SW defects and anticancer medicines, which are important to the delivery process, were investigated in depth. The adsorption energies of the NU and TP drug molecules on the ABNNR-SW defect are much greater than those of the other complex structures with the Eads, which are − 30.667 and − 30.473 eV, respectively. This is a consequence of the Stone-Wales impact on the ABNNR structure, according to the results. In terms of specific drug delivery and biomedicine, the recovery period value indicates that ABNNR-SW is more suitable as a carrier for the NU and TP drugs, respectively. [ABSTRACT FROM AUTHOR]

Single-image super-resolution (SISR) techniques have found wide applications in semiconductor defect inspection. Enhancing image resolution to improve inspection sensitivity and accuracy holds great significance. A novel SISR algorithm, called cross-convolutional residual network (CCRN), is proposed in this study. CCRN comprises a cross-convolutional module (CCM), which incorporates a cross-sharing mechanism that facilitates the fusion of features from different stages, enabling the extraction of more information from the image. Moreover, a global residual aggregation structure (GRA) is introduced. GRA captures and transfers different levels of residual features acquired from learning each CCM to the reconstruction layer. Experimental results demonstrate that the proposed SR algorithm outperforms existing state-of-the-art SR algorithms in terms of both visual and quantitative metrics when applied to optical, SEM, and TEM images of microfluidic chips, CMOS image sensors, and quantum dots, respectively. Additionally, CCRN significantly improves the accuracy of defect classification and inspection of unpatterned wafers, as evaluated using the WM-811K dataset. Notably, an increase in local defection testing accuracy from 79.00% to 89.00% and an improvement in classification accuracy from 93.69% to 96.06% are achieved. These findings underscore the potential applications of the proposed algorithm in improving semiconductor defect inspection and classification accuracies. [ABSTRACT FROM AUTHOR]

We report an easy-to-fabricate microcavity design to produce optically pumped high-β quantum dot microlasers. Our cavity concept is based on a buried photonic-defect for tight lateral mode confinement in a quasi-planar microcavity system, which includes an upper dielectric distributed Bragg reflector (DBR) as a promising alternative to conventional III–V semiconductor DBRs. The cavities show distinct emission features with a characteristic photonic-defect size-dependent mode separation and Q-factors up to 17 000. Comprehensive investigations further reveal lasing operation with a systematic increase (decrease) of the β-factor (threshold pump power) with the number of mirror pairs in the upper dielectric DBR. Notably, due to the quasi-planar device geometry, the microlasers show high temperature stability, evidenced by the absence of temperature-induced redshift of emission energy and linewidth broadening typically observed for nano- and microlasers at high excitation powers. The device exhibits remarkable lasing performance, maintaining efficacy even under elevated temperatures of up to 260 K. [ABSTRACT FROM AUTHOR]

Ultrawide bandgap semiconductors (UWBGs) provide great promise for optical devices operating in the near to deep ultraviolet, and recently they have become a viable semiconducting material for high power electronics. From the power grid to electronic vehicles, the intention is to replace massively awkward components with the convenience of a solid state electronic "chip." Unfortunately, the challenges faced by wide bandgap electronic materials, such as GaN and SiC, increase as the bandgap increases. A point defect, for example, can take on more charge states and energy configurations. This perspective describes a method to investigate the many charge states and their associated transitions—photo-induced electron paramagnetic resonance (photo-EPR) spectroscopy. Although not new to the study of defects in semiconductors, photo-EPR studies can probe the entire ultrawide bandgap given the appropriate light source for excitation. Examples provided here cover specific defects in UWBGs, AlN, and Ga2O3. The discussion also reminds us how the rapid pace of discovery surrounding this newest class of semiconductors is due, in part, to fundamental research studies of the past, some as far back as a century ago and some based on very different materials systems. [ABSTRACT FROM AUTHOR]

While Ta3N5 shows excellent potential as a semiconductor photoanode for solar water splitting, its performance is hindered by poor charge carrier transport and trapping due to native defects that introduce electronic states deep within its bandgap. Here, it is demonstrated that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep‐level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti4+ ions substitute Ta5+ lattice sites, thereby introducing compensating acceptor states, reducing the concentrations of deleterious nitrogen vacancies and reducing Ta3+ states, and thereby suppressing trapping and recombination. Owing to the similar ionic radii of Ti4+ and Ta5+, substitutional doping does not introduce lattice strain or significantly affect the underlying electronic structure of the host semiconductor. Furthermore, Ti can be incorporated without increasing the oxygen donor content, thereby enabling the electrical conductivity to be tuned by over seven orders of magnitude. Thus, Ti doping of Ta3N5 provides a powerful basis for precisely engineering its optoelectronic characteristics and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications. [ABSTRACT FROM AUTHOR]

This study investigates the shape complexity of hydrogenic impurity states in the Ga1 − χAlχN semiconductor quantum well for the first time. The shape complexity is calculated for a specific hydrogenic impurity state in both position and momentum spaces (C[r] and C[p]) through the utilization of Shannon entropy and averaging electron probability density. The results demonstrate that the Shannon entropy and the average electron probability density vary monotonically with the quantum well width. However, the shape complexity exhibits extreme points, and their physical source is discussed in detail. Furthermore, the impact of doping Al element on the shape complexity of the hydrogenic impurity in the Ga1 − χAlχN quantum well is examined. The investigation demonstrates that the changes in C[r] or C[p] with the quantum well width exhibit similarity for different contents of the doping Al element, indicating a scaled invariance of shape complexity under translation. However, for a fixed width of the quantum well, the shape complexity of hydrogenic impurity state in the Ga1 − χAlχN quantum well is highly sensitively to the Al element content. As the shape complexity plays a crucial role in quantifying the disorder of a quantum system, our findings indicate that we can control the internal disorder of hydrogenic impurity in the semiconductor quantum well by adjusting the well size and doping element content. Our study provides some theoretical guidance for the study of the internal disorder of hydrogenic impurity in semiconductor quantum well and has certain applications in semiconductor material manufacturing and synthesis. [ABSTRACT FROM AUTHOR]

Electrically detected magnetic resonance (EDMR) is arguably the most sensitive method available to study electrically active point defects in semiconductor devices. Most EDMR studies have utilized spin-dependent recombination current and, thus, require p–n junctions or a photoconductive structure. Some time ago, Chen and Lang proposed and demonstrated EDMR via spin-dependent deep level transient spectroscopy in metal–oxide–semiconductor capacitors. We report on a similar and significantly simpler technique: spin-dependent transient spectroscopy (SDTS). We show that the sensitivity of this technique is independent of the resonance field and frequency. Through capacitance–voltage analysis, combined with our SDTS results, this technique can (crudely) provide information about the density of states of defects with a broad distribution of energy levels. In addition, we show that SDTS can be readily adapted to near-zero-field magnetoresistance effect measurements. [ABSTRACT FROM AUTHOR]

Both the static and kinetic properties of defects play fundamental roles in determining the physical properties of semiconductors. Compared to the static properties of defects, a comprehensive understanding of the different defects diffusing in different types of semiconductors is still lacking. In this article, based on extensive first-principles calculations, we have done a comparative study on the diffusion mechanisms of point defects in Si (a typical elemental semiconductor) and GaN (a typical compound semiconductor). The significantly different diffusion mechanisms of vacancies and interstitials in Si and GaN result in significantly different recombination mechanisms, i.e., a novel synergistic effect to accelerate the annihilation of defects is observed in Si but not in GaN, indicating that an efficient self-recovery mechanism can exist in Si but not in GaN. Our results not only explain some experimental observations in Si and GaN under nonequilibrium irradiation conditions but also provide a good example to understand the different kinetic properties of defects in elemental and compound semiconductors. [ABSTRACT FROM AUTHOR]

The laser heterodyne photothermal displacement (LH-PD) method was used to characterize the nonradiative recombination centers of semiconductors, such as defects and deep-lying electronic levels. When a semiconductor surface is irradiated with a modulated continuous wave laser, the irradiated area is periodically heated and expanded owing to the nonradiative recombination of the photoexcited carriers. The LH-PD can measure an absolute value of surface displacement and its time variation at various excitation beam frequencies ( f e x ). Si and GaAs substrate samples were used to confirm the usefulness of the proposed method. The obtained time variation of the surface displacement was well explained by theoretical calculations considering the carrier generation, diffusion, recombination, heat diffusion, and generated thermal strain. Because nonradiative carrier recombination generates local heat at defects in semiconductors, the LH-PD technique is useful for analyzing defect distributions. Additionally, measurements of intentional Fe-contaminated Si samples confirmed that this technique is suitable for defect mapping. Displacement mapping with changing f e x suggests the potential to measure the distribution of nonradiative recombination centers in the sample depth direction. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) is an insulator that has shown little promise to be converted to a semiconductor via impurity doping. Some of the historic challenges for successfully doping AlN include a reconfigurable defect formation known as a DX center and subsequent compensation that causes an increase in dopant activation energy resulting in very few carriers of electricity, electrons, or holes, rendering doping inefficient. Using crystal synthesis methods that generate less compensating impurities and less lattice expansion, thus impeding the reconfiguration of dopants, and using new dopants, we demonstrate: (a) well behaved bulk semiconducting functionality in AlN, the largest direct bandgap semiconductor known with (b) substantial bulk p-type conduction (holes = 3.1 × 1018 cm-3, as recently reported in our prior work), (c) dramatic improvement in n-type bulk conduction (electrons = 6 × 1018 cm-3, nearly 6000 times the prior state-of-the-art), and (d) a PN AlN diode with a nearly ideal turn-on voltage of ~6 V for a 6.1 eV bandgap semiconductor. A wide variety of AlN-based applications are enabled that will impact deep ultraviolet light-based viral and bacterial sterilization, polymer curing, lithography, laser machining, hightemperature, high-voltage, and high-power electronics. [ABSTRACT FROM AUTHOR]

The CdIn2S4 semiconductor is considered a potential host for the implementation of intermediate band solar cells due to its ideal bandgap value and excellent photoelectric property. In this paper, the electronic structures of group IV elements (Si, Ge, Sn, and Pb)-doped CdIn2S4 have been investigated by using hybrid density functional calculations. In the case of Ge, Sn, and Pb doping, an isolated and partially occupied intermediated band with delocalized characteristics could be created in the bandgap of the host. The results of the projected density of states reveal that the intermediated band is derived from the hybridization between the S-3p and dopant-ns states. Thanks to the assistance of the impurity band, the optical absorption ability of the intermediate band semiconductor is greatly enhanced. Based on the detailed balance theory, the theoretical efficiencies of intermediate band solar cells made by Ge- and Pb-doped CdIn2S4 are estimated to be 45.0% and 49.2%, respectively, which are superior to the Shockley and Queisser limit (40.7%) of a single junction photovoltaic device. Moreover, the experimental synthesis of these impurity semiconductors is relatively feasible because substitutional doping at the octahedral position is energetically favorable. These findings would be helpful to the development of a high-efficiency intermediate band solar cell. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of one-dimensional (1-D) hydrogenic impurity in Nitride semiconductor quantum well have been investigated. Firstly, using a combination of the linear variational approach and the effective mass approximation, we obtain the eigen-energy of hydrogenic impurity states in AlN, GaN and InN quantum wells. Subsequently, we explore the quantum size effect on the thermodynamic properties of these low-dimensional semiconductor structures, revealing some novel and intriguing phenomena. It is found as the width of the quantum well is increased, the energy of hydrogenic impurity gets decreased, however, the thermodynamic parameters, such as the average energy, entropy and heat capacity of the hydrogenic impurity become increased. The physical origins of these peculiar phenomena are attributed to the competitive mechanism between the quantum confinement effect and Coulombic interaction between the electron and impurity. Finally, by conducting a comprehensive comparison of the thermodynamic parameters among GaN, InN, and AlN quantum wells, we propose an innovative strategy for modulating the thermodynamic properties of these low-dimensional semiconductor structures. This manipulation can be achieved not only through external factors such as temperature and quantum well size, but also by altering internal variables like the effective mass and relative dielectric constant of the semiconductor material. This study not only advances our understanding of the thermodynamic properties of hydrogenic impurities in semiconductor quantum wells, but also provides some theoretical guidance for practical applications in fields such as semiconductor physics, condensed matter physics, chemical physics, etc. [ABSTRACT FROM AUTHOR]

Spin defects in semiconductors have demonstrated promising electronic structures for potential applications in quantum computing and sensing. Among various proposed quantum byte systems, spin defects in silicon carbide have attracted significant attention due to several advantages they offer over other options. In this study, we investigate carbon-antisite-vacancy defects in 4H silicon carbide through ab initio density functional theory calculations. With the HSE06 functionals, the ab initio computation can predict much more accurate electronic structures. However, the corresponding computational cost is high, especially for supercells consisting of several hundreds of atoms. In this investigation, the carbon-antisite-vacancy defect is studied by using a high-performance computing cluster, with a specific focus on supercells that encompass two such defects. The extension of a single carbon-antisite-vacancy defect is depicted by referring to the spin density distribution. Different defect types show similar spin density patterns. Based on the single defect characteristics, supercells with paired carbon-antisite-vacancy defects are created. It is found that the binding energy can reach 2 eV for overlapping defects. In the case of insignificant overlap of the corresponding single defects, the ground state magnetic moment is 4 µB, accompanied by a negligible binding energy. However, if there is a significant overlap of the spin density, the magnetic moment changes to 2 µB. These findings can serve as helpful references for the study of spin defects in 4H silicon carbide, particularly in the potential carbon-antisite-vacancy application research. [ABSTRACT FROM AUTHOR]

Various secondary particles are emitted when the surface of solid matter is irradiated with ions. This phenomenon has been utilized in several methods to analyze target materials. In analytical techniques, the method used to detect secondary ions is called "secondary ion mass spectrometry (SIMS)." In contrast, "secondary ion mass spectrometry with optical emission spectrometry (SIMS‐OES)" detects photons emitted from sputtered, excited atoms. Both SIMS and OES can characterize a sample surface and perform local elemental analysis of the surface, depth profiling of elements, and detection of any atom. SIMS with high sensitivity has mainly been developed for the impurity analyses of semiconductors. However, no research has been reported on applications using SIMS‐OES or a combination of SIMS and SIMS‐OES. In this study, we prove that atomic emission can be observed via ion irradiation. In addition, we show that the composition analysis is possible using the SIMS‐OES method. Herein, impurity and composition analyses were enabled by utilizing atomic emission. Moreover, we proved that an assessment with high‐depth direction resolution is feasible by etching the circumference of a crater in advance. [ABSTRACT FROM AUTHOR]

A series of carbon-doped ZnO [Zn1−yCyO (0.00 ≤ y ≤ 0.10)] nanorods were synthesized using a cost-effective low-temperature (85 °C) dip coating technique. X-ray diffractometer scans of the samples revealed the hexagonal structure of the C-doped ZnO samples, except for y = 0.10. XRD analysis confirmed a decrease in the unit cell volume after doping C into the ZnO matrix, likely due to the incorporation of carbon at oxygen sites (CO defects) resulting from ionic size differences. The morphological analysis confirmed the presence of hexagonal-shaped nanorods. X-ray photoelectron spectroscopy identified C–Zn–C bonding, i.e., CO defects, Zn–O–C bond formation, O–C–O bonding, oxygen vacancies, and sp2-bonded carbon in the C-doped ZnO structure with different compositions. We analyzed the deconvoluted PL visible broadband emission through fitted Gaussian peaks to estimate various defects for electron transition within the bandgap. Raman spectroscopy confirmed the vibrational modes of each constituent. We observed a stronger room-temperature ferromagnetic nature in the y = 0.02 composition with a magnetization of 0.0018 emu/cc, corresponding to the highest CO defects concentration and the lowest measured bandgap (3.00 eV) compared to other samples. Partial density of states analysis demonstrated that magnetism from carbon is dominant due to its p-orbitals. We anticipate that if carbon substitutes oxygen sites in the ZnO structure, the C-2p orbitals become localized and create two holes at each site, leading to enhanced p–p type interactions and strong spin interactions between carbon atoms and carriers. This phenomenon can stabilize the long-range order of room-temperature ferromagnetism properties for spintronic applications. [ABSTRACT FROM AUTHOR]

A formula is proposed for calculating the spectral position of the peak of the nonphonon line (zero phonon line, ZPL) of donor–acceptor (DA) photoluminescence in p- and n-type covalent semiconductors with hydrogen-like impurities at low temperatures and low levels of steady-state interband photoexcitation. The model uses a nonstoichiometric simple cubic impurity lattice formed jointly by doping (majority) and compensating (minority) impurity atoms in the crystal matrix. It is assumed that the distribution densities of energy levels of donors forming the D0-band and energy levels of acceptors forming the A0-band in the band gap of the crystal are Gaussian with equal root-meansquare fluctuations of the ionization energy. Nonphonon radiative DA-recombination is considered to occur only between nearest neighbors in the impurity lattice upon a nonequilibrium electron transition from the energy level of the first excited state of donor to the acceptor energy level in the A0-band, which coincides with the Fermi level in this band in a p-type semiconductor or upon a nonequilibrium hole transition from the energy level of the first excited state of acceptor to the donor energy level in the D0-band, which coincides with the Fermi level in the band in an n-type semiconductor. The calculated dependence of the maximum of DA-photoluminescence nonphonon line on the concentration and degree of compensation of majority impurities by minority impurities is consistent with known experimental data for neutron-transmutation doped germanium crystals. [ABSTRACT FROM AUTHOR]

A quasi-classical model for calculating DC (direct current) electrical conductivity in crystalline semiconductors with hydrogen-like impurities is developed at the transition from band conduction to impurity hopping conduction with decreasing temperature. This transition from the minimum band conductivity to the maximum hopping conductivity via impurities has the form of a characteristic "kink" in the temperature dependence of the electrical resistivity. The idea of the calculation is to preliminarily determine the transition temperature Tj using the standard approach within the framework of the two-band model. The shift of the top of the -band (the bottom of the c-band) into the depth of the band gap due to the formation of a quasi-continuous band of allowed energy values from the excited states of acceptors (donors) is taken into account. This leads to a decrease in the value of a thermal ionization energy of the majority shallow impurities due to a decrease in the maximum localization radius of a hole on an acceptor (an electron on a donor) with increasing impurity concentration. The values of the observed maximum hopping conductivity and drift hopping mobility corresponding to the temperature Tj are calculated. The numerical calculation within the framework of the proposed model is consistent with the known experimental data on the electrical conductivity and Hall co efficient of moderately compensated p-Ge crystals doped by neutron transmutation and non-intentionally compensated metallurgically doped n-Ge, as well as n- and p-Si crystals on the insulator side of the Mott insulator-metal concentration phase transition. [ABSTRACT FROM AUTHOR]

In the field of semiconductor defect inspection, detecting defects with high accuracy is possible owing to the object detection model (defect detector) composed of the deep learning model. On the other hand, the performance of the deep learning model depends highly on training data. Therefore, during the operational phase at the customer site, we need to frequently evaluate the model’s performance to deal with shifts in appearance for defects. However, frequently executing general evaluation methods is difficult at the customer site. Hence, we need a method to automatically evaluate performance. In this study, for the purpose of automatically evaluating the performance of the defect detector, we propose Positive/Negative Decision via Outlier Detection (PNDOD). The PNDOD decides on the positive of negative for each detection result based on comparing features corresponding to the detected result with statistics computed from training data. Using this method, we can calculate the estimated precision from the ratio of the estimated number of positive detections to the number of total detections, and we can evaluate the performance automatically based on it. Through experiments, we confirm the PNDOD can decide on the positive or negative with high accuracy, and we can precisely evaluate the model’s performance. [ABSTRACT FROM AUTHOR]

A series of carbon-doped ZnO [Zn1−yCyO (0.00 ≤ y ≤ 0.10)] nanorods were synthesized using a cost-effective low-temperature (85 °C) dip coating technique. X-ray diffractometer scans of the samples revealed the hexagonal structure of the C-doped ZnO samples, except for y = 0.10. XRD analysis confirmed a decrease in the unit cell volume after doping C into the ZnO matrix, likely due to the incorporation of carbon at oxygen sites (CO defects) resulting from ionic size differences. The morphological analysis confirmed the presence of hexagonal-shaped nanorods. X-ray photoelectron spectroscopy identified C–Zn–C bonding, i.e., CO defects, Zn–O–C bond formation, O–C–O bonding, oxygen vacancies, and sp2-bonded carbon in the C-doped ZnO structure with different compositions. We analyzed the deconvoluted PL visible broadband emission through fitted Gaussian peaks to estimate various defects for electron transition within the bandgap. Raman spectroscopy confirmed the vibrational modes of each constituent. We observed a stronger room-temperature ferromagnetic nature in the y = 0.02 composition with a magnetization of 0.0018 emu/cc, corresponding to the highest CO defects concentration and the lowest measured bandgap (3.00 eV) compared to other samples. Partial density of states analysis demonstrated that magnetism from carbon is dominant due to its p-orbitals. We anticipate that if carbon substitutes oxygen sites in the ZnO structure, the C-2p orbitals become localized and create two holes at each site, leading to enhanced p–p type interactions and strong spin interactions between carbon atoms and carriers. This phenomenon can stabilize the long-range order of room-temperature ferromagnetism properties for spintronic applications. [ABSTRACT FROM AUTHOR]