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The development of kesterite photovoltaic solar cells has been hindered by large open-circuit voltage (Voc) deficit. Recently, SnZn deep point defect and associative defect cluster have been recognized as the main culprit for the Voc losses. Therefore, manipulating the deep-level donor of SnZn antisite defects is crucial for breaking through the bottleneck of present Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic technology. In this study, the SnZn deep traps in CZTSSe absorber layer are suppressed by incorporation of Ge. The energy levels and concentration of SnZn defects measured by deep-level transient spectroscopy (DLTS) decrease significantly. In addition, the grain growth of CZTSSe films is also promoted due to Ge implantation, yielding the high quality absorber layer. Consequently, the efficiency of CZTSSe solar cells increases from 9.15% to 11.48%, largely attributed to the 41 mV Voc increment.

Unabated, worldwide trends in CO2 production project growth to > 43-BMT per year over the next two decades. Efficient power electronics are crucial to fully realizing the CO2 mitigating benefits of a worldwide smart grid (~ 18% reduction for the United States alone). Even state-of-the-art SiC high voltage junction devices are inefficient because of slow transition times (~ 0.5-μs) and limited switching rates at high voltage (~ 20-kHz at ≥ 15-kV) resulting from the intrinsically limited charge carrier drift speed (7-cm-s−1). Slow transition times and limited switch rates waste energy through transition loss and hysteresis loss in external magnetic components. Bulk conduction devices, where carriers are generated and controlled nearly simultaneously throughout the device volume, minimize this loss. Such devices are possible using below bandgap excitation of semi-insulating (SI) SiC single crystals. We explored carrier dynamics with a 75-fs single wavelength pump/supercontinuum probe and a modified transient spectroscopy technique and also demonstrated a new class of efficient, high-speed, high-gain, bi-directional, optically-controlled transistor-like power device. At a performance level six times that of existing devices, for the first time we demonstrated prototype operation at multi-10s of kW and 20-kV, 125-kHz in a bulk conduction transistor-like device using direct photon-carrier excitation with below bandgap light.

The pressure-dependent optoelectronic properties of all-inorganic perovskite CsPbBr3 nanocrystals (NCs) are investigated with steady-state and transient spectroscopy. The steady-state absorption an...

Global economies are transitioning towards net-zero emissions, but technological leaps are still needed to accelerate decarbonisation within the energy sector and beyond. Here, several novel material systems are studied to uncover physical properties which will dictate their suitability for use in state-of-the-art light-harvesting structures such as thin-film photovoltaics and photoelectrochemical fuel cells. Such materials offer promising avenues to cheap and efficient sustainable energy solutions. Metal halide perovskites excel in the pursuit of highly efficient thin film photovoltaics and light emitters. Substitution of the monovalent cations has advanced luminescence yields and device efficiencies. In this thesis, the change in photocarrier recombination behaviour caused by cation alloying is explored. Time-resolved optical spectroscopy and microscopy are used to reveal local charge accumulation in mixed cation perovskites, creating p- and n-type photodoped regions, unearthing a strategy for efficient light emission at low charge-injection in solar cells and light-emitting diodes. Operational stability of perovskite solar cells remains a barrier to their commercialisation, yet a fundamental understanding of degradation processes, including the specific sites at which failure mechanisms occur, is lacking. Here, multimodal microscopy techniques are utilised to show that nanoscale defect clusters, which are associated with phase impurities, are sites at which material degradation seeds. The trapping of charge carriers at sites associated with phase impurities, itself reducing performance, catalyses redox reactions that compromise device longevity. Importantly, this reveals that both performance losses and intrinsic degradation can be mitigated by eliminating these defective clusters. Carbon nanodots are an emergent material whose ease of fabrication and water solubility make them exciting candidates for photocatalytic processes. However, a full understanding of their excited charge carrier dynamics and interaction with common electron donors/acceptors is not yet established. This work identifies charge transfer processes in hybrid photocatalytic systems with carbon nanodot absorbers and builds bottom-up mechanistic insight., The author acknowledges support from the Engineering and Physical Sciences Research Council (EPSRC) and the Japan Society for the Promotion of Science (JSPS)

The trapping characteristics of point defects in CdZnTe crystals grown by the vertical Bridgman method (VB) and the traveling heater method (THM) were analyzed. The photo-induced current transient spectroscopy (PICTS) was used to determine the traps’ energy, their capture cross-section and concentration. Moreover, the trapping and de-trapping times of point defects were obtained. Furthermore, the photoconductive technology under sub-bandgap illumination were employed to study the influence of the trapping characteristics on mobility-lifetime (μτ) product of CdZnTe crystal. The quantitative results indicated that sub-bandgap illumination can effectively improve carrier mobility-lifetime. The deep levels (TeCd), which occupy the position around the midgap, with high de-trapping time and low trapping time have greater effect on μτ product for the crystals than Cd vacancies. The Te secondary-phase related defects, which can be observed in the VB method grown crystals, have less influence on μτ product than Te antisite.

The formidable rise of lead‐halide perovskite photovoltaics has energized the search for lead‐free perovskite‐inspired materials (PIMs) with related optoelectronic properties but free from toxicity limitations. The photovoltaic performance of PIMs closely depends on their defect tolerance. However, a comprehensive experimental characterization of their defect‐level parameters—concentration, energy depth, and capture cross‐section—has not been pursued to date, hindering the rational development of defect‐tolerant PIMs. While mainstream, capacitance‐based techniques for defect‐level characterization have sparked controversy in lead‐halide perovskite research, their use on PIMs is also problematic due to their typical near‐intrinsic character. This study demonstrates on four representative PIMs (Cs3Sb2I9, Rb3Sb2I9, BiOI, and AgBiI4) for which Photoinduced Current Transient Spectroscopy (PICTS) offers a facile, widely applicable route to the defect‐level characterization of PIMs embedded within solar cells. Going beyond the ambiguities of the current discussion of defect tolerance, a methodology is also presented to quantitatively assess the defect tolerance of PIMs in photovoltaics based on their experimental defect‐level parameters. Finally, PICTS applied to PIM photovoltaics is revealed to be ultimately sensitive to defect‐level concentrations

Defects in the semiconductor structure of a photovoltaic converter (PVC) with a p–n junction and antireflection film of porous silicon manufactured using chemical stain etching were studied by the current deep-level transient spectroscopy technique. The influence of the regime of porous silicon film formation on the transformation of deep-level defects and the main PVC characteristics is explained.

A measuring system for current deep-level transient spectroscopy of semiconductor diode structures is described. Its distinguishing feature is the ability to measure several relaxation currents (up to eight current dependences for one temperature scanning) at different regimes of deep-level recharging. The structural features of the system for measuring and analyzing the temperature dependence of the relaxation current in semiconductor structures are described.

Electronic traps are the primary factor stifling the performance of quantum-dot (QD) solar cells to nearly half their theoretical potential. Yet, the exact origin of these traps remains largely unknown, making it difficult to address the problem. In the inaugural issue of Matter, Gilmore et al. employ advanced transient spectroscopy to reveal that QD dimerization can be as detrimental as unpassivated surface states in QD films.

Device structures with silicon or germanium nanodots embedded in an oxide matrix may find application in the field of Non-Volatile Memories (NVMs) [1,2] or photonics [3,4]. In the former case, the nanodots can become charged by tunneling of electrons or holes from the silicon substrate through a tunnel oxide. Successful operation requires that the charge does not leak away by the assistance of traps or defects in the material stack. The latter can be probed by techniques like Admittance Spectroscopy [5] or Deep-Level Transient Spectroscopy (DLTS) [2,5]. In the present work we report on a systematic investigation of Metal-Oxide-Semiconductor (MOS) capacitors fabricated on n-type Czochralski silicon substrates and containing Ge nanodots with different size. Ge nanodots with average diameter of 1, 2 or 3 nm have been deposited by Molecular Beam Epitaxy (MBE) on a 5 nm tunnel oxide, thermally grown on n-type Czochralski silicon wafers. An Atomic Force Microscopy (AFM) picture is shown in Fig. 1. Next, 50 nm of SiO2 is deposited. MOS capacitors are prepared by thermal evaporation of 2 mm diameter Al gate contacts, while InGa+In foil ohmic contacts are prepared on the silicon substrate side. The device structure is schematically shown in Fig. 2. Capacitance-Voltage (C-V) characterization is performed at a fixed frequency f=1 MHz, using both a forward and reverse gate voltage sweep. As can be seen in Fig. 3, the presence of the Ge nanodots has a pronounced impact on the C-V characteristics: there is a shift towards positive flat-band voltage, compared with the zero dot reference, a strong increase of the accumulation capacitance and, for the nanodot samples, the hysteresis increases with the increase in nanodot size. For temperature (T-) scan DLTS, the capacitors are mounted in a helium contact gas cryostat cooled with liquid nitrogen. Measurements at different bias pulses from reverse bias (VR) to the pulse bias (VP) are performed in parallel in order to probe the electron traps in different parts of the structure. An example is given in Fig. 4, for the 1 nm nanodots sample. It shows that in deep depletion, there is a broad peak between 150-250 K which could stem from the response of filled interface traps. The increase found at room temperature may originate from minority carrier generation in the depletion region [2,5,6]. When probing closer to the interface, for more positive VR, a pronounced but broad peak around 200 K dominates the spectra. From the Arrhenius plot shown in Fig. 5, it is concluded that it corresponds to the dangling bond (Pb) acceptor level at about 0.31 eV from the conduction band [2,5,6]. Maximum densities are estimated in the range of 5x1011 cm-2eV-1. A comparison of the spectra near the interface for the different samples studied is provided in Fig. 6 and will be discussed in more detail in the conference paper. References [1] S. Tiwari, H. Hanafi, A. Hartstein, E.F. Crabbe and K. Chan, Appl. Phys. Lett., 68, 1377 (1996). [2] R. Beyer, J. von Borany and H. Burghardt, Microelectron. Eng., 86, 1859 (2009). [3] J. von Borany, R. Grötzschel, K.H. Heinig, A. Markwitz, W. Matz, B. Schmidt and W. Skorupa, Appl. Phys. Lett., 71, 3215 (1997). [4] D.A. Grachev, A.V. Ershov, A.V. Belolipetsky, L.V. Krasilnikova, A.N. Yablonskiy, B.A. Andreev and O.B. Gusev, Phys. Stat. Sol. A, 213, 2867 (2016). [5] E. Simoen, J. Lauwaert and H. Vrielinck, Semiconductors and Semimetals, Eds. L. Romano, V. Privitera and C. Jagadish, 91, pp. 205-250, Elsevier 2015. [6] S.N. Volkos, E.S. Efthymiou, S. Bernardini, I.D. Hawkins, A.R. Peaker and G. Petkos, J. Appl. Phys., 100, 124103 (2006). Figure 1

InP- and GaAs-based metamorphic In 0.83 Ga 0.17 As photodetectors were grown and investigated. Compared to InP-based photodetector, the dark current of GaAs-based photodetector at room temperature increased 2–3 times but still comparable, whereas at 77 K the dark current increased 2–3 orders. The deep-level transient spectroscopy results reveal that a deep level trap state exists in the GaAs-based photodetector structure. The higher dark current in GaAs-based photodetector at low temperature was mainly ascribed to a deep level trap induced tunneling current. The deep trap centers can also induce non-radiative recombination with smaller thermal active energy in the GaAs-based photodetector structure.

We have studied changes of sub-gap defect states in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) by means of photoinduced transient spectroscopy (PITS). It is found that the sub-gap states in the channel region of a-IGZO TFTs were drastically modified as back-channel etch process proceeded. The change was due to in-and out-diffusion of hydrogen atoms in the channel region of a-IGZO TFTs, which affects the performance of the a-IGZO TFTs.

Electron traps are detected from vertical n+-GaAs/n−-InGaP/p+-GaAs diodes with deep-level transient spectroscopy (DLTS). Combining lock-in window (t w ) varying DLTS and double-correlation DLTS (DDTLS), we assign the electron traps to surface states at the sidewalls of the diodes. The methodology is introduced in the paper.

International audience; It is shown that deep level transient spectroscopy can be carried out on Schottky diodes to investigate, in addition to majority carrier traps, minority carrier traps. This is possible thanks to the application of a large reverse bias to the device which allows minority carrier injection by lowering their corresponding effective Schottky barrier height. Indeed, when increasing the reverse bias voltage, the deep level transient spectroscopy signal, initially negative and thus showing only majority carrier traps signature, becomes positive, revealing minority carrier traps involvement. A careful analysis of the recorded spectra leads to the identification of four minority carrier traps which have been so far only evidenced using dedicated technique such as minority carrier transient spectroscopy.

Defects in a semiconductor structure of a photoelectric converter of solar energy based on a p–n junction with an antireflection film of porous silicon on the front surface have been studied by current deeplevel transient spectroscopy. An explanation of the influence of thickness of a porous-silicon film formed by electrochemical etching on the character of transformation of defects with deep levels and efficiency of solarenergy conversion is proposed.

Interface traps (ITs) and border traps (BTs) in Al2O3/GeOx/p-Ge gate stacks were characterized using deep-level transient spectroscopy. Through evaluating the gate stacks with different GeOx thicknesses, the respective BTs in Al2O3, the Al2O3/GeOx interface region, and GeOx were detected. The density of ITs (Dit) near the midgap is lower in the metal-oxide-semiconductor (MOS) capacitors with thicker GeOx, while Dit near the valence band is lower in the MOS capacitor with thinner GeOx. The density of BTs (Nbt) in Al2O3 (6–9 × 1017 cm−3) is lower than those in GeOx (∼2 × 1018 cm−3), and the highest Nbt (∼1 × 1019 cm−3) was found in the Al2O3/GeOx interface region. Ge p-channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) with Al2O3/GeOx/p-Ge gate stacks were fabricated and analyzed. We confirmed that the ITs and the BTs near the valence band edge of Ge affect the effective mobility of Ge p-MOSFETs in the high-field region.

We present preliminary results on minority carrier traps in as-grown n-type 4H&ndash, SiC Schottky barrier diodes. The minority carrier traps are crucial for charge trapping and recombination processes. In this study, minority carrier traps were investigated by means of minority carrier transient spectroscopy (MCTS) and high-resolution Laplace-MCTS measurements. A single minority carrier trap with its energy level position at Ev + 0.28 eV was detected and assigned to boron-related defects.

In this paper, we have investigated the trapping phenomenon in AlInN/GaN HEMTs using the drain current transient spectroscopy. From the trapping and detrapping drain current transient analysis under different biasing conditions, energy levels and locations of associated traps are extracted. Surface traps with activation energy of ~0.18 eV and buffer traps of energy ~0.27 eV were identified from this analysis. Hopping conduction of trapped surface electrons are also identified from this study.

In this work, deep levels present in n-type In0.53Ga0.47As hetero-epitaxial layers grown lattice-matched on n-type InP substrates by molecular beam epitaxy have been studied by deep-level transient spectroscopy (DLTS). Metal–oxide–semiconductor capacitors are employed, based on an Al2O3 gate oxide. It is shown that a single, near mid-gap electron trap dominates the DLT-spectra, whatever the surface pre-or post-gate oxide deposition treatment. At the same time, it is shown that the deep level parameters vary significantly from capacitor to capacitor and from wafer to wafer. Only after Forming Gas Annealing, a stable value for the activation energy of 0.39 ± 0.01 eV is obtained. These results are tentatively interpreted in terms of antisite defects in the epitaxial layer, which form a family of related complexes with close deep-level parameters.

An overview is given on how to tackle the question of the electrical activity of extended defects which are inevitably present in hetero-epitaxial III-V layers on silicon. Analysis methods are described which rely on simple device structures containing a specific type of extended defect (here, threading dislocations). Applying the same methods to real scaled FinFETs is rather challenging. Instead Generation-Recombination noise spectroscopy provides data that can be compared with other more standard techniques, like Deep-Level Transient Spectroscopy (DLTS) in order to identify the presence of an electrically active extended defect in the channel material.

Time-resolved spectroscopy is a powerful tool for studying fundamental photophysics in optoelectronic materials on a molecular temporal scale. In this review, we describe transient spectroscopic studies on fundamental photovoltaic conversion processes in polymer solar cells, which consist of a series of conversion processes such as photon absorption, exciton diffusion into a donor/acceptor interface, charge transfer at the interface, charge dissociation into free charge carriers, and charge collection to each electrode. These conversion processes are ultrafast phenomena and are ranging over the wide temporal scale from femtoseconds to microseconds, which can be directly observed by transient spectroscopy.

The specific features of detecting the contribution of the characteristic intrinsic defect in semi-insulating GaAs to photocurrent relaxation are considered. A detailed analysis of the relaxation kinetics based on approximation by the sum of exponential components is presented. The approximation results are compared with the data of photo-induced current transient spectroscopy.

Electrical characteristics of low-Mg-doped p-Al0.02–0.07Ga0.98–0.93N and p-In0.02Ga0.98N Schottky contacts were investigated. A memory effect was revealed in the current–voltage (I–V) characteristics, which is found also in p-GaN contacts and may be due to charge and discharge of holes to acceptor-type interfacial defects. High-temperature isothermal transient spectroscopy revealed that the defect densities in the Al0.02Ga0.98N and In0.02Ga0.98N samples were nearly half that in the GaN samples. A large reverse current with a memory effect was observed in the In0.02Ga0.98N contacts. It was suggested that current can flow via relatively shallow acceptor-type interfacial defects. For the AlxGa1−xN with x = 0.04 and 0.07, I–V characteristics became leaky. The Schottky barrier heights estimated from the photoresponse experiment were higher than the values estimated from the bandgap by 0.19, 0.21, 0.20, and 0.21 eV for Al0.02Ga0.98N, Al0.04Ga0.96N, Al0.07Ga0.93N, and In0.02Ga0.98N samples, respectively. A probable explanation for such discrepancies may be due to the total charge amount of the interfacial states, which varied the electric field and the barrier lowering. It was found that even though the Al or In content was only as small as 2%, the electrical characteristics of the contacts changed significantly.

To model drain IV characteristics, the temperature dependence is important for GaN HEMT. We show that the time dependence should also be included in the modeling approach. In this paper, we use the trap information obtained from current transient spectroscopy (CTS) to create a 3D plot of I ds -V ds -time(I-V-t). This gives a more realistic description for time-domain pulsed IV behavior. The controversial question of whether the pulsed IV/RF is a trapping effect or a thermal effect is analyzed. The Poole-Frenkel emission-based time-dependent trapping model is proposed to describe the GaN HEMT memory effects (kink effect and knee walkout). To our knowledge, this is the first model offered to describe the “soft” (or degraded) knee region of the GaN HEMT IV curves.

In this work we present a detailed study of the influence of the GaAs substrate orientation on the electrical properties of heterojunctions based on GaAs and sulfonated polyaniline (SPAN) using Current-Voltage (I-V), Capacitance-Voltage (C-V), Deep-Level Transient Spectroscopy (DLTS) and Laplace DLTS techniques. Three different GaAs substrate orientations have been investigated, namely (1 0 0), (3 1 1)A and (3 1 1)B. The I-V results revealed that the turn-on voltage (Von) of SPAN/(3 1 1)B GaAs heterojunction is higher than that for SPAN/(1 0 0) GaAs and SPAN/(3 1 1)A GaAs heterojunctions. The DLTS results showed that the number of electrically active defects present in devices based on the lower index (1 0 0) plane of GaAs substrate is higher than those of higher index (3 1 1)A and (3 1 1)B GaAs substrates, corroborating with I-V results. In order to investigate the role of interface states, capacitance-frequency measurements were performed in forward bias on all three devices.

The results of investigations of the pyroelectric current in a layered TlInS2 crystal doped with lanthanum are presented. A comparative analysis of the obtained results and data of photo-induced current transient spectroscopy has been performed. The revealed features of the contribution from electrically active defects to pyroelectric properties of the crystal have been discussed.

Photoinduced current transient spectroscopy has been used in studying deep-level defects of the ferroelectric-semiconductor TlInS2. The specific features of defect detection in the lanthanum-doped and undoped single crystals have been compared. The explanation of the decrease in the photoelectric activity of defects in the doped sample has been proposed.

Pulsed-laser deposited ZnO thin films were implanted with Ar-ions to generate intrinsic defects within the material. The defects created were analyzed by deep-level and optical deep-level transient spectroscopy. Deep-level defects with thermal activation energies of 980 and appear after implantation. In order to study the annealing behavior of these defects, the implanted samples were isochronously annealed under an oxygen ambient of at temperatures ranging from 120 to . Both defects are annealed out after annealing for 1 h at . (O)DLTS signal of an 40Ar-implanted ZnO thin film under (a) dark condition and (b) under illumination with photons having a wavelength of .

While carbon doping is known to increase the resistivity of GaN, highly resistive layers for device isolation can also be obtained by ion implantation. In this study, we report on the electrical characterization of C-implanted n-type homoepitaxial GaN. Our investigation, carried out by capacitance-voltage measurements and deep level/minority carrier transient spectroscopy, revealed the presence of nine majority carrier traps in the 0.2–1.3 eV energy range, below the conduction band edge, and of four minority carrier traps, in the 0.1–1.4 eV energy range, above the valence band edge. The net-donor compensation mechanism and the behavior of defect centers are studied as a function of the annealing temperature in the 100–1000 °C range. While the former is explained in terms of dynamic annealing, the latter is discussed in the light of the present experimental results and those found in the literature.

The authors use isothermal capacitance transient spectroscopy to detect three deep defects located at approximately 0.6, 0.8, and 1.0 eV below the conduction band of β-Ga2O3 materials. The electrical properties of these defects such as their capture cross sections and concentrations are characterized, and their potentially adverse effects on power electronic devices are discussed. Because the isothermal capacitance transient spectroscopy method is implementable by instruments intended for steady-state capacitance-voltage measurement, it is promising for use as an effective characterization and monitoring tool for deep defects in β-Ga2O3 and other wide bandgap semiconductors.

We have investigated the electrical properties of a ZnO microwire grown by carbo-thermal evaporation, a ZnO thin film grown by pulsed-laser deposition on an a-plane sapphire, and a hydrothermally grown Zn-face ZnO single crystal (Tokyo Denpa Co. Ltd.). The samples were investigated by means of current-voltage measurements, capacitance-voltage measurements, and deep-level transient spectroscopy.The defects T2 [1,2] and E3 [1,3,4] were identified in all three sample types. Additionally, in the single crystal and thin film samples E64 [5] and E4 [1] were detected. These findings support the common opinion that T2 is an intrinsic defect since it is found in all the samples investigated and thus its occurrence is not related to any growth technique.

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φb) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.

Electrical properties of a ZnO microwire grown by carbo-thermal evaporation, a ZnO thin film grown by pulsed-laser deposition and a hydrothermally grown ZnO bulk crystal are compared. Deep defects were investigated by means of deep-level transient spectroscopy. The defect level E3 was observed in all samples investigated. Additionally, a defect labelled T2 that preferentially forms under Zn-rich condition was detected in the microwire, the thin film and the bulk sample. Our results indicate that V Zn is likely involved in this defect.

Despite the astonishing values of the power conversion efficiency reached, in just less than a decade, by the carbon nanotube/silicon (CNT/Si) solar cells, many doubts remain on the underlying transport mechanisms across the CNT/Si heterojunction. Here, by combining transient optical spectroscopy in the femtosecond timescale, X-ray photoemission, and a systematic tracking of I–V curves across all phases of the interlayer SiOx growth at the interface, we grasp the mechanism that adequately preserves charge separation at the junction, hindering the photoexcited carrier recombination. Moreover, supported by ab initio calculations aimed to model the complex CNT–Si heterointerface, we show that oxygen-related states at the interface act as entrapping centers for the photoexcited electrons, thus preventing recombination with holes that can flow from Si to CNT across the SiOx layer.

The aim of this paper is to give an extensive presentation of the defect-related degradation of InGaN-based laser diodes (LDs) submitted to constant current stress, at room temperature. The analysis is based on combined electrical-optical characterization, the capacitance-temperature analysis, and deep-level transient spectroscopy (DLTS). The results show that stress induces a significant increase of the threshold current and the appearance of two defects, possibly related to point defects arranged along lines.

We investigated trap levels in detector-grade CdZnTe (CZT) material grown by using three different methods, viz, the Bridgman, traveling heater method (THM), and high-pressure Bridgman method (HPB), by current deep-level transient spectroscopy (I-DLTS). All CZT detectors contained deep trap levels located at around 1.1 eV (which we designated DE1), which has been attributed to Te vacancies induced one. However, our crystal growth and characterization results indicated that dislocations induced by Te secondary defects (inclusions/precipitates)were a more probable origin than Te vacancies. Also, a theoretical calculation of the electron de-trapping time associated with DE1 can explain well the abnormal residual current behavior at temperatures slightly above room temperature. Our results show better control of the concentrations and the sizes of Te secondary defects is critical to improving the detector’s performance at room temperature by reducing lagging effects.

Electrically active defects in silicon-based epitaxial layers on silicon substrates have been studied by Deep-Level Transient Spectroscopy (DLTS). Several aspects have been investigated, like, the impact of the pre-epi cleaning conditions and the effect of a post-deposition anneal on the deep-level properties. It is shown that the pre-cleaning thermal budget has a strong influence on the defects at the substrate/epi layer interface. At the same time, a post-deposition Forming Gas Anneal can passivate to a large extent the active defect states. Finally, it is shown that application of a post-deposition anneal increases the out-diffusion of carbon from a Si:C stressor layer into the p-type CZ substrate.

In this paper a systematic and detailed study on the photophysical behavior of silicon nanocrystals (alkyl-capped, surface oxidized, oxide-encapsulated) is presented in order to elucidate the influence of local environment and surface species on the luminescence properties. Experiments at different temperatures – ranging from room temperature (RT) to 7 K – confirmed the important influence of the silicon nanocrystal (ncSi) surface on the photoluminescence (PL). Our comparative study of ncSi embedded in different matrices shows a strong increase of the exciton lifetimes at low temperature and the dominant widening of the bandgap for small ncSi after deactivation of traps below 100–150 K. The present findings have significant implications for the use of ncSi in optoelectronic and biomedical applications, since they show that surface oxidation can occur in ligand-capped ncSi which limits the accessible emission wavelength for these applications to the orange/red spectral region when current passivation strategies are used.

Temperature dependent capacitance-voltage (C-V) and constant capacitance transient spectroscopy (CCDLTS) measurements have been performed to investigate the role of N in improving the transport properties of 4H-SiC MOS transistors. The higher channel mobility in the N pre-implanted transistors is due at least in part to activation of a small fraction of the implanted N near the SiO2/SiC interface as donors in SiC during oxidation, thus reducing the effects of interface trapping. In addition, the absence of oxidation-induced near-interface defects, which were observed in NO-annealed capacitors, may contribute to the improved mobility in N pre-implanted transistors.

Deep-level transient spectroscopy (DLTS) has been used to study p-n junctions fabricated by implantation of boron into epitaxial 4H-SiC films with n-type conductivity and the donor concentration (8–9) × 1014 cm−3. A DLTS signal anomalous in sign is observed; this signal is related to recharging of deep compensating boron-involved centers in the n-type region near the metallurgical boundary of the p-n junction.

The charge compensation in undoped GaP single crystals is investigated by modeling the Fermi level position for various concentrations of shallow and deep donors and acceptors. The model is based on the numerical solution of the charge neutrality equation and allows for calculating the Fermi energy in the temperature range of 1 –1000 K. The experimental studies of the electronic properties and concentrations of grown-in defect centers are performed by the high-resolution photoinduced transient spectroscopy (HRPITS). We show that at the shallow acceptor concentration below 1x1015 cm-3 and the concentration of deep-level defects ~3x1015 cm-3 obtaining undoped GaP with the semi-insulating (SI) properties is possible by substantial reducing the residual concentration of shallow donor impurities.

As-grown and annealed Ga0.6In0.4N0.005As0.995/GaAs with 1, 3, and 7 quantum well structures grown by Molecular Beam Epitaxy (MBE) are investigated using Photoluminescence (PL) and Photo-Induced Current Transient Spectroscopy (PICTS) measurements in order to determine the effects of the number of quantum wells and thermal annealing on optical properties and qualities of the structures. PICTS results reveal that all the samples with different quantum well numbers have two dominate trap levels which related to GaInNAs layer. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In the present paper, 4H-SiC JBS diodes with "boron" p–n junctions have been investigated by means of deep-level transient spectroscopy (DLTS). The sign of the DLTS signal for all the 4H-SiC diodes under study, was positive. The "anomaly" of the DLTS spectra measured is apparently connected with the properties of "boron" p–n junctions. In particular, is presented the role of deep D-centers in recompensation of donors in the JBS diodes.