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We investigate the native point defects in the long-wavelength infrared (LWIR) detector material H g 0.75 C d 0.25 Te using a dielectric-dependent hybrid density functional combined with spin–orbit coupling. Characterizing these point defects is essential as they are responsible for intrinsic doping and nonradiative recombination centers in the detector material. The dielectric-dependent hybrid functional allows for an accurate description of the bandgap (E g) for Hg 1 − x Cd x Te (MCT) over the entire compositional range, a level of accuracy challenging with standard hybrid functionals. Our comprehensive examination of the native point defects confirms that cation vacancies V Hg (Cd) are the primary sources of p -type conductivity in the LWIR material given their low defect formation energies and the presence of a shallow acceptor level (− /0) near the valence-band maximum. In addition to the shallow acceptor level, the cation vacancies exhibit a deep charge transition level (2 − / −) situated near the midgap, characteristic of nonradiative recombination centers. Our results indicate that Hg interstitial could also be a deep center in the LWIR MCT through a metastable configuration under the Hg-rich growth conditions. While an isolated Te antisite does not show deep levels, the formation of V Hg –Te Hg defect complex introduces a deep acceptor level within the bandgap. [ABSTRACT FROM AUTHOR]

This work investigates the structural properties of HgCdTe thin films grown on InSb (211)B substrates using molecular beam epitaxy (MBE). The Cd composition of thin films is accurately determined using non-destructive approaches based on x-ray diffraction (XRD) and reflectance infrared spectroscopy. The as-grown HgCdTe thin films exhibit characteristic surface defects with a size of 7–10 μm and density of ∼105 cm−2, resulting in an additional spread in XRD full width at half maximum. Cross-sectional transmission electron microscopy results indicate that these defects are caused by surface In droplet formation during the oxide removal process of InSb substrate, which subsequently results in the formation of In4Te3 inclusions and extended defects in MBE-grown HgCdTe. Our findings provide additional confirmation that suppressing thermally induced damage of the InSb substrate is necessary for fabricating high-performance infrared detectors using HgCdTe grown on InSb substrates. [ABSTRACT FROM AUTHOR]

Herein, in order to successfully create high-density La 0.67 Ca 0.33- x Sr x MnO 3 : Ag 0.15 (LCSMO: Ag) ceramics (0 ≤ x ≤ 0.05), this research combines sol-gel and solid-phase processes. LCSMO: Ag ceramics electrical transport and magnetic properties were thoroughly investigated. XRD verified that the high-purity orthorhombic perovskite structure (space group Pnma) was produced. As Sr doping rises, the grain size grows, the single electron bandwidth increases, the metal-insulator transition temperature (T MI) continues to climb, and temperature coefficient of resistance (TCR) and magnetoresistance (MR) steadily drop. When x = 0.04, the T MI reaches 302.2 K. At this time, the TCR peak (TCR peak) reaches 24.0 %·K−1 and the MR peak reaches 49.2 %. These results demonstrate that Sr may effectively raise the T MI of LCMO: Ag ceramics to room temperature while maintaining high TCR and MR Values, which benefits the material's potential applications in devices such as uncooled infrared detectors. [ABSTRACT FROM AUTHOR]

2D black phosphorus (b‐P) possesses several remarkable properties, including ambipolar transport, high carrier mobility, in‐plane anisotropy, polarization sensitivity, a narrow direct bandgap that can be tuned with the number of layers, and highly compatible with silicon‐based technologies. These characteristics make it a promising material for photodetection in the near‐infrared to mid‐infrared range. However, to date, most of the reviews on b‐P are centered around electronic and optoelectronic devices, with few specifically addressing infrared detection. Herein, the recent research progress on b‐P infrared detectors is summarized in this review. This article introduces the principle of optoelectronic detection, the main properties of 2D b‐P, the development history of b‐P fabrication methods, presents and discusses the performance and characteristics of various infrared photodetectors based on different structures of 2D b‐P that have been researched in recent years. Finally, the challenges that may be faced by black phosphorus‐based infrared photoelectric detectors are briefly introduced, and the potential application directions are discussed from the perspective of large‐scale production and practical application. This article provides an in‐depth analysis and evaluation of the future development prospects of 2D b‐P materials as a potential excellent candidate of infrared photodetectors. [ABSTRACT FROM AUTHOR]

High‐resolution infrared (IR) imaging technology holds substantial significance across diverse fields including biomedical imaging, environmental surveillance, and IR digital cameras. Current IR detectors used in commercial applications are based on ultra‐high vacuum‐processed traditional inorganic semiconductors like silicon or III‐V compounds (e.g., Si, Ge, and InGaAs). However, the rapid advancements in applications such as autonomous vehicles, virtual reality, and point‐of‐care healthcare are driving an escalating need for innovative imaging technologies. This review aims to bridge the gap by exploring solution‐processed semiconductor photodetectors (PDs), which offer distinct advantages including cost‐effectiveness, tunable spectral response, and potential for multiple‐exciton generation. These characteristics make them particularly suitable for optical communication, IR imaging, and biological monitoring applications. This review provides comprehensive insights into the research trends pertaining to solution‐processed IR detectors and imagers based on colloidal quantum dots, perovskites, organic compounds, and 2D materials. The review commences with the current market worth of image sensors, the fundamental principles of single‐pixel and multipixel array IR imagers, and key parameters used to assess IR detector performance. In essence, the review concludes with a summary of recent advancements and future prospects for next‐generation IR PD devices and their potential application as an IR imager. [ABSTRACT FROM AUTHOR]

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The well-known Rule07 is a simple thus efficient way to compare available technologies for IR imaging detectors in terms of dark current. The noise is then often estimated using a shot noise approximation on the dark current. Both II–VI and III–V communities use this rule of thumb as a reference for well-performing IR photodiodes. For HOT applications, a dark current close to this rule07 is considered a necessary condition but not a sufficient one to obtain a high-performance IR imager. Indeed, when limited by shot noise, rule07 describes well the noise behavior of the considered device. However, when considering low-frequency noise, it fails to describe the expected performances. In this paper, we focus on another figure-of-merit, dedicated to detector low-frequency noise rather than dark current. Systemic 1/f noise investigation in an IR detector was first reported by Tobin et al. in 1980. There is today a relative consensus on the fact that measured 1/f noise is proportional to the dark current. The ratio between the amplitude of the 1/f noise and the dark current of the same devices may therefore be used as a figure-of-merit for a given technology. This ratio (called the Tobin factor α T ) therefore appears adequate to compare different technologies as a figure-of-merit qualifying 1/f noise properties. This dimensionless ratio can also be very useful for optimizing a particular technology or process. However, in order to be relevant, this figure-of-merit must be estimated carefully as it appears, for instance, pixel pitch-dependent. Different examples of Tobin coefficient extraction are presented in this paper. We show that, depending on the technologies, the values of the Tobin coefficient can spread over several orders of magnitude. However, only low values result in high-quality IR imagers. Today, the best results we obtained show that α T = 10 - 5 is a state-of-art value to be compared with. [ABSTRACT FROM AUTHOR]

HgCdTe epilayers grown by chemical vapor deposition (MOCVD) on GaAs substrates operating in the long-wave infrared range were characterized by the photoluminescence (PL) method. Photodiode and photoconductor designs, both (100) and (111)B crystallographic, were analyzed. Spectral current responsivity (RI) and a PL signal approximated by a theoretical expression being the product of the density of states and the Fermi–Dirac distribution were used to determine the fundamental transition (energy gap, Eg). For all the samples, an additional deep-level-related transition associated with mercury vacancies (VHg) were observed. The energy distance of about 80 meV above the valence band edge was observed for all the samples. Moreover, measurements at low temperature showed shallow acceptor-level (AsTe and VHg as acceptors) transitions. In HgCdTe(100), due to the higher arsenic activation, AsTe was the dominant acceptor dopant, while, in HgCdTe(111)B, the main acceptor level was formed by the neutral VHg. The determined activation energies for AsTe and VHg dopants were of about 5 meV and 10 meV, respectively. [ABSTRACT FROM AUTHOR]

Photopyroelectric‐based circularly polarized light (CPL) detection, coupling the pyro‐phototronic effect and chiroptical phenomena, has provided a promising platform for high‐performance CPL detectors. However, as a novel detection strategy, photopyroelectric‐based CPL detection is currently restricted by the short‐wave optical response, underscoring the urgent need to extend its response range. Herein, visible‐to‐near‐infrared CPL detection induced by the pyro‐phototronic effect is first realized in chiral‐polar perovskites. Specifically, chiral‐polar multilayered perovskites (S‐BPEA)2FAPb2I7 (1‐S, S‐BPEA = (S)‐1‐4‐Bromophenylethylammonium, FA = formamidinium) with spontaneous polarization shows intrinsic pyroelectric and photopyroelectric performance. Strikingly, combining its merits of the pyro‐phototronic effect and intrinsic wide‐spectrum spin‐selective effect, chiral multilayered 1‐S presents efficient photopyroelectric‐based broadband CPL detection performance spanning 405–785 nm. This research first realizes photopyroelectric‐based infrared CPL detection and also sheds light on developing high‐performance broadband CPL detectors based on the pyro‐phototronic effect in the fields of optics, optoelectronics, and spintronics. [ABSTRACT FROM AUTHOR]

The demand for miniaturized and integrated multifunctional devices drives the progression of high‐performance infrared photodetectors for diverse applications, including remote sensing, air defense, and communications, among others. Nonetheless, infrared photodetectors that rely solely on single low‐dimensional materials often face challenges due to the limited absorption cross‐section and suboptimal carrier mobility, which can impair sensitivity and prolong response times. Here, through experimental validation is demonstrated, precise control over energy band alignment in a type‐II van der Waals heterojunction, comprising vertically stacked 2D Ta2NiSe5 and the topological insulator Bi2Se3, where the configuration enables polarization‐sensitive, wide‐spectral‐range photodetection. Experimental evaluations at room temperature reveal that the device exhibits a self‐powered responsivity of 0.48 A·W−1, a specific directivity of 3.8 × 1011 cm·Hz1/2·W−1, a response time of 151 µs, and a polarization ratio of 2.83. The stable and rapid photoresponse of the device underpins the utility in infrared‐coded communication and dual‐channel imaging, showing the substantial potential of the detector. These findings articulate a systematic approach to developing miniaturized, multifunctional room‐temperature infrared detectors with superior performance metrics and enhanced capabilities for multi‐information acquisition. [ABSTRACT FROM AUTHOR]

During infrared detection, the thermal radiation from the background generates substantial photon noise and thus severely limit the capability of an infrared detector to identify a target. Going beyond this limitation has been a long‐standing challenge in the development of infrared detectors. This paper proposes to break this limitation by creating a narrow photoresponse band with a high peak responsivity to reject the background radiation and enhance the responsivity to the target with characteristic emission lines. This scheme is numerically demonstrated in a dimerized grating integrated quantum well infrared photodetector, based on critical coupling with a Brillouin zone folding induced quasi‐bound state in the continuum (BIC). The asymmetric deformation of the grating structure folds the photonic band and generates a quasi‐BIC with a tunable high radiation Q factor (QR) at the Γ point. By reducing the doping concentration of the quantum wells for a high absorption Q factor (QA) and tuning the QR to make QR = QA for critical coupling, a narrowband photoresponse with a high peak responsivity is achieved and the background‐limited specific detectivity of 4.55 × 1012 cm Hz1/2 W−1 is obtained for a 2π field of view, surpassing the ideal‐photoconductor limit by 92 times. [ABSTRACT FROM AUTHOR]

Effective suppression of dark current is essential for improving the performance of bulk defect-mediated absorption (BDA) photodetectors. Blocked impurity band (BIB) infrared detectors have been developed and utilized from mid-infrared to far-infrared wavelength regions for low noise. In this work, a blocking layer of dark current was applied to a BDA short-wave infrared (SWIR) photodetector, emulating the concept of BIB detectors. ZnO was chosen as the blocking layer to impede the transport of electrons from the bulk defect levels due to its wide bandgap and to allow the photocurrent to remain nearly unaffected by proper positioning of the conduction band minimum. After introducing the ZnO blocking layer, the dark current density of the photodetector was reduced by two orders of magnitude, and the specific detectivity was enhanced by one order of magnitude. The effects of TiO2 and WO3 as blocking layers were also investigated and compared with ZnO. This work offers an effective method for enhancing detectivity in SWIR BDA photodetection by suppressing the dark current efficiently. [ABSTRACT FROM AUTHOR]

Blackbody‐sensitive uncooled infrared photodetectors with ultra‐broadband and ultrafast photoresponse have a profound impact on many areas of modern science and technology. However, it is a big challenge for both traditional photodetectors and emerging low‐dimensional ones to simultaneously have all the above characteristics. Here, this challenge is addressed by establishing a Te/WTe2 heterostructure photodetector. The built‐in field of the heterostructure and the crossing conduction and valence bands of WTe2 jointly result in a high responsivity and a visible‐to‐long‐wavelength‐infrared photoresponse range. The peak responsivity (at the 3.3 µm wavelength) reaches 914 mA W−1 at zero bias and 8.51 A W−1 at 2 V bias. Further, the joint action coupled with the high mobility of Te and WTe2 promotes the 3‐dB bandwidth to 153 kHz. The self‐powered blackbody responsivity and specific detectivity reach 235.7 mA W−1 and 1.1 × 108 cm Hz1/2 W−1, respectively. The former increases to 5.82 A W−1 at 1 V bias. Moreover, this device is polarization‐sensitive with a contrast ratio of 2. This work reveals the potential of the Te/WTe2 heterostructure for high‐performance room‐temperature infrared photodetectors. [ABSTRACT FROM AUTHOR]

An ultrasensitive photothermal assay was designed for point-of-care testing (POCT) of tumor markers based on a filter membrane. Firstly, Cu2-xSe was successfully encapsulated in liposome spheres with biotin on the surface and connected to carcinoembryonic antigen (CEA) aptamer with 3'end modified biotin by streptavidin. Secondly, the CEA antibody was successfully modified on the surface of the nitrocellulose membrane through simple incubation. Finally, the assay process was completed using a disposable syringe, and the temperature was recorded using a handheld infrared temperature detector. In the range 0–50 ng mL−1, the temperature change of the nitrocellulose membrane has a strong linear relationship with CEA concentration, and the detection limit is 0.097 ng mL−1. It is worth noting that the entire testing process can be easily performed in 10 min, much shorter than traditional clinical methods. In addition, this method was successfully applied to the quantitative determination of CEA levels in human serum samples with a recovery of 96.2–103.3%. This rapid assay can be performed by "one suction and one push" through a disposable syringe, which is simple to operate, and the excellent sensitivity reveals the great potential of the proposed strategy in the POCT of tumor biomarkers. [ABSTRACT FROM AUTHOR]

This review explores the integration of graphene and liquid crystals to advance sensor technologies across multiple domains, with a focus on recent developments in thermal and infrared sensing, flexible actuators, chemical and biological detection, and environmental monitoring systems. The synergy between graphene's exceptional electrical, optical, and thermal properties and the dynamic behavior of liquid crystals leads to sensors with significantly enhanced sensitivity, selectivity, and versatility. Notable contributions of this review include highlighting key advancements such as graphene-doped liquid crystal IR detectors, shape-memory polymers for flexible actuators, and composite hydrogels for environmental pollutant detection. Additionally, this review addresses ongoing challenges in scalability and integration, providing insights into current research efforts aimed at overcoming these obstacles. The potential for multi-modal sensing, self-powered devices, and AI integration is discussed, suggesting a transformative impact of these composite sensors on various sectors, including health, environmental monitoring, and technology. This review demonstrates how the fusion of graphene and liquid crystals is pushing the boundaries of sensor technology, offering more sensitive, adaptable, and innovative solutions to global challenges. [ABSTRACT FROM AUTHOR]

The long-wave infrared (LWIR) interband cascade detector with type-II superlattices (T2SLs) and a gallium-free ("Ga-free") InAs/InAsSb (x = 0.39) absorber was characterized by photoluminescence (PL) and spectral response (SR) methods. Heterostructures were grown by molecular beam epitaxy (MBE) on a GaAs substrate (001) orientation. The crystallographic quality was confirmed by high-resolution X-Ray diffraction (HRXRD). Two independent methods, combined with theoretical calculations, were able to determine the transitions between the superlattice minibands. Moreover, transitions from the trap states were determined. Studies of the PL intensity as a function of the excitation laser power allowed the identification of optical transitions. The determined effective energy gap (Eg) of the tested absorber layer was 116 meV at 300 K. The transition from the first light hole miniband to the first electron miniband was red-shifted by 76 meV. The detected defects' energy states were constant versus temperature. Their values were 85 meV and 112 meV, respectively. Moreover, two additional transitions from acceptor levels in cryogenic temperature were determined by being shifted from blue to Eg by 6 meV and 16 meV, respectively. [ABSTRACT FROM AUTHOR]

• Combining multistage thermoelectric cooler with infrared detectors for analysis. • Finite rate heat transfer irreversibility is considered and a finite time thermodynamic model of a heat-pipe-type four-stage thermoelectric cooler is developed. • New evaluation indexes are proposed: module utilization coefficient and coordination performance coefficient. • Heat pipe is used to enhance heat transfer and improve the performance of the thermoelectric cooler. • Large temperature difference cooling to meet the requirements of detectors is achieved. A cooler provides a low-temperature working environment for refrigerated infrared detection chips and is an indispensable component in infrared detectors that ensures their smooth operation. In this paper, a thermodynamic model of a heat-pipe-type four-stage thermoelectric cooler with a large temperature difference applied to a focal plane infrared detector is constructed. The heat leakage of the detector is calculated using the model. The performance indexes of the coordination performance coefficient and module utilization coefficient are used to unify the cooling capacity and economic performance of the device. The impression of the working current, heat pipe parameters, and cross-sectional area of the thermoelectric leg on the performance of cooler are analyzed. A Pareto optimal solution is obtained using an NSGA-II algorithm and TOPSIS decision. A low cooling temperature is obtained using a multistage thermoelectric cooler to achieve a large cooling temperature difference. When the working current is 5.65 A and the cross-sectional area is 4.5 mm2, the maximum cooling temperature difference reaches 110.6 °C, and the lowest cooling temperature reaches -83.6 °C. When the working temperature of the detector is -60 °C, the current and cross-sectional area corresponding to the optimal solution of cooling capacity-COP-power consumption are 1.51 A and 2.74 mm2, respectively. [ABSTRACT FROM AUTHOR]

Pyroelectric materials have been widely studied because of their important role in infrared detectors, sensors, thermal imaging, and other applications, among which, lead-based ceramics are extensively adopted. However, the environmental problems caused by lead-based compounds in production and processing are becoming increasingly serious. Meanwhile, the surface mounting technology is extensively employed in the electronics industry for device miniaturization and integration. However, due to its high processing temperature (∼260 °C), it makes most pyroelectric ceramic materials unsuitable for this process. Therefore, it is of great significance to develop novel high-performance lead-free pyroelectric ceramics with high depolarization temperature (>260 °C). In this work, we report the Na0.995Ag0.005NbO3-0.1%Mn (NANM) pyroelectric ceramics. The antiferroelectric–ferroelectric phase transition field and coercive field of NaNbO3 ceramics were reduced by the introduction of AgNbO3 and Mn, making it easier to induce the ferroelectric phase and realize poling in NANM ceramics. The NANM ceramics exhibited an excellent pyroelectric coefficient of 2.55 × 10−4 C m−2 K−1 and figures of merit as Fi = 0.93 × 10−10 m/V, Fv = 6.46 × 10−2 m2/C, and Fd = 2.92 × 10−5 Pa−1/2 at room temperature. More importantly, a high depolarization temperature of 280 °C was achieved, ensuring the ability to withstand high temperature during production and operation. The NANM ceramics with excellent pyroelectric properties and high depolarization temperature are expected to be a promising lead-free candidate for uncooled infrared detector applications. [ABSTRACT FROM AUTHOR]

Acquiring multi-dimensional optical information, such as intensity, spectrum, polarization, and phase, can significantly enhance the performance of photodetectors. Incorporating these dimensions allows for improved image contrast, enhanced recognition capabilities, reduced interference, and better adaptation to complex environments. However, the challenge lies in obtaining these dimensions on a single photodetector. Here we propose a misaligned unipolar barrier photodetector based on van der Waals heterojunction to address this issue. This structure enables spectral detection by switching between two absorbing layers with different cut-off wavelengths for dual-band detection. For polarization detection, anisotropic semiconductors like black phosphorus and black arsenic phosphorus inherently possess polarization-detection capabilities without additional complex elements. By manipulating the crystal direction of these materials during heterojunction fabrication, the device becomes sensitive to incident light at different polarization angles. This research showcases the potential of the misaligned unipolar barrier photodetector in capturing multi-dimensional optical information, paving the way for next-generation photodetectors. Multi-dimensional detection of optical information with a single device enables energy- and area-efficient sensing capabilities. Here, the authors report dual-band infrared detectors based on misaligned 2D black phosphorus and black arsenic phosphorus, sensitive to light intensity, spectrum and polarization. [ABSTRACT FROM AUTHOR]

The response of a DPbS3200 infrared detector irradiated by a nanosecond pulsed laser and CW laser has been investigated to study laser-induced interference. A laser interference experiment system was constructed to measure the time-varying response signal. A nanosecond pulsed laser and a CW laser of 10 Hz were used, with a 1064 nm wavelength and a millimeter-scale irradiation spot diameter. Firstly, the characteristics of transient interference signals induced by pulsed lasers were analyzed. Then, the characteristics of response signal interference by both CW laser and pulsed laser irradiation were further investigated. The results showed that the pulsed laser only produced transient interference. However, the CW laser led to a significant amplitude reduction of the response signal, which could continuously interfere in the operating time. For transient interferences, the amplitude of the interference signal increased linearly with the laser fluence. The relation between the pulse repetition rate of the incident laser and the operating frequency of the detector determined the numbers of transient interference signals in one response period; for the interference induced by both the CW laser and pulsed laser, CW laser interference played a leading role when CW laser power density increased to 4.1 W/cm2 or more. As the CW laser fluence reached 6.1 W/cm2, the PbS infrared detector was no longer able to detect any signal, which caused temporary blindness. In the end, a probit model was used to determine the interference threshold. [ABSTRACT FROM AUTHOR]

Filter elements based on metamaterial structure are one of the essential schemes for researching the miniaturization of spectral detection systems. The aim of this study is to meet the application requirements of different long-wave infrared signal frequency filtering and improve the detection efficiency of micro-filters. In this paper, a periodic micro-nano-cross-linked hole structure is designed, based on the surface plasmonic polariton resonance effect to realize the extraordinary optical transmission performance of 8 ~ 12 μm long-wave infrared. Based on the surface plasmonic polariton excitation mechanism of periodic micro-nano-structures, the tunable performance of the transmission spectra at five central wavelengths of 8, 9, 10, 11, and 12 μm was achieved by changing the simulation period and the overall period of the model, and the optimal peak transmittance was 88.31% with a half-wave width of 1.31 ± 0.01 μm. The present study summarizes the tuning mode and rule of the micro-nano-cross-linked structure to realize the blue/redshift under the performance of the extraordinary optical transmission, which provides an important reference for the miniaturized structure design of infrared spectral detectors and tunable filtering research and is conducive to the application of broadband filtering spectral chips. [ABSTRACT FROM AUTHOR]

Passive imaging for mid-wave infrared (MWIR) is resistant to atmospheric pollutants, guaranteeing image clarity and accuracy. Arrayed photodetectors can simultaneously perform radiation sensing to improve efficiency. Room temperature van der Waals (vdWs) photodetectors without lattice matching have evolved rapidly with optimized stacking methods, primarily for single-pixel devices. The urgent need to implement arrayed devices aligns with practical demands. Here, we present an 8 by 1 black phosphorus/molybdenum sulfide (BP/MoS2) vdWs photodetector linear array with a fill-factor of ~77%, fabricated using a temperature-assisted sloping transfer method. The flat interface and uniform thickness facilitate carrier transport and minimize pixel nonuniformities, showing an average peak detectivity (D*) of 2.34 × 109 cm·Hz1/2·W-1 in the mid-wave infrared region. Compared to a single pixel, push-broom scanning passive imaging is eight times more efficient and further enhanced through mean filtering and fast Fourier transform filtering for strip noise correction. Our study offers guidance on vdWs arrayed devices for engineering applications. [ABSTRACT FROM AUTHOR]

This article investigates the effect of hydrostatic pressure on the optoelectronic characteristics of the InAsNBi/InAs quantum well (QW) system using an expanded version of the standard 8-band k dot p Hamiltonian. The effect of hydrostatic pressure on important structural and electronic parameters such as elastic constants, band gap, band offset, band structure, and effective masses are investigated in this manuscript. These factors assisted in the computation of optical gain spectra for different quantum well structures. Furthermore, this study is extended to several heterostructures by including diverse barrier materials such as GaAs, GaSb, and InP with InAsNBi QW. The optical analysis of these heterostructures can help the researchers to design and fabricate optoelectronic devices that can operate in LWIR regimes owing to the narrow bandgap of quaternary InAsNBi. Additionally, we examined the optical characteristics in TE mode for variations in hydrostatic pressure. [ABSTRACT FROM AUTHOR]

Triglycine sulfate (TGS) crystals are pyroelectric crystals that exhibit ferroelectricity in a room-temperature environment. They have application as infrared detector elements. In this study, it was found that irradiation with 40-GHz electromagnetic waves accelerates the growth of TGS crystals, with a growth rate about 2.2 times faster than that without irradiation. This leads to a reduction in process time and therefore crystals that will be used as elements in the production of detectors can be obtained more quickly. The TGS crystals were irradiated with a CO2 laser at a wavelength of 10.6 μm. The maximum voltage value obtained was about 0.24 V, the photosensitivity was 24.7 V/W, and the noise equivalent power (NEP) was 2.7 × 10−8 W/Hz½. In addition, it was confirmed that the sensitivity increased with decreasing area of the crystal. These results show that TGS crystals grown under electromagnetic irradiation can be used as infrared detector elements. [ABSTRACT FROM AUTHOR]

Pyroelectric materials, with piezoelectricity and pyroelectricity, have been widely used in infrared thermal detectors. In this paper, a modified first-order plate theory is extended to analyze a pyroelectric sensitive element structure. The displacement, temperature, and electric potential expand along the thickness direction. The governing equation of the pyroelectric plate is built up. The potential distributions with upper and lower electrodes are obtained under different supported boundary conditions. The corresponding numerical results of electric potential are consistent with those obtained by the three-dimensional finite element method. Meanwhile, the theoretical results of electric potential are close to that of experiments. The influence of supported boundary conditions, piezoelectric effect, and plate thickness are analyzed. Numerical results show that the piezoelectric effect reduces the electric potential. The thickness of the pyroelectric plate enhances the electric potential but reduces the response speed of the detector. It is anticipated that the pyroelectric plate theory can provide a theoretical approach for the structural design of pyroelectric sensitive elements. [ABSTRACT FROM AUTHOR]

This paper introduces a cost-effective, high-performance approach to achieving wafer level vacuum packaging (WLVP) for MEMS-based uncooled infrared sensors. Reliable and hermetic packages for MEMS devices are achieved using a cap wafer that is formed using two silicon wafers, where one wafer has precise grating/moth-eye structures on both sides of a double-sided polished wafer for improved transmission of over 80% in the long-wave infrared (LWIR) wavelength region without the need for an AR coating, while the other wafer is used to form a cavity. The two wafers are bonded using Au-In transient liquid phase (TLP) bonding at low temperature to form the cap wafer, which is then bondelectrical and Electronics d to the sensor wafer using glass frit bonding at high temperature to activate the getter inside the cavity region. The bond quality is assessed using three methods, including He-leak tests, cap deflection, and Pirani vacuum gauges. Hermeticity is confirmed through He-leak tests according to MIL-STD 883, yielding values as low as 0.1 × 10−9 atm·cc/s. The average shear strength is measured as 23.38 MPa. The package pressure varies from 133–533 Pa without the getter usage to as low as 0.13 Pa with the getter usage. [ABSTRACT FROM AUTHOR]

We describe a novel ultrahigh vacuum state-to-state molecule/surface scattering apparatus with quantum state preparation of the incident molecular beam and angle-resolved quantum state detection of the scattered molecules. State-resolved detection is accomplished using a tunable mid-infrared laser source combined with a cryogenic bolometer detector and is applicable to any molecule with an infrared-active vibrational transition. Results on rotationally inelastic scattering of CH4 methane from a Ni(111) surface and NiO(111)/Ni(111) oxide film, obtained by the new apparatus, are presented. Molecules scattering from the oxidized surface, compared to those scattering from the bare nickel surface, are more highly excited rotationally and scatter into a broader distribution of angles. The internal alignment of molecular rotation is in addition found to be stronger in molecules scattering from the bare surface. Furthermore, the maxima of the state-resolved angular distributions shift toward and away from surface normal with increasing rotational quantum number J for the oxidized and bare surface, respectively. Finally, the rotational state populations produced in scattering from the oxidized surface are well-described by a Boltzmann distribution, while those produced in scattering from the bare surface exhibit large deviations from their best-fit Boltzmann distributions. These results point toward a marked enhancement in molecule–surface collisional energy exchange induced by oxidation of the nickel surface. [ABSTRACT FROM AUTHOR]

In the field of electronic and optoelectronic applications, two-dimensional materials are found to be promising candidates for futuristic devices. For the detection of infrared (IR) light, MoTe2 possesses an appropriate bandgap for which p-MoTe2/n-Si heterojunctions are well suited for photodetectors. In this study, a rapid thermal technique is used to grow MoTe2 thin films on silicon (Si) substrates. Molybdenum (Mo) thin films are deposited using a sputtering system on the Si substrate and tellurium (Te) film is deposited on the Mo film by a thermal evaporation technique. The substrates with Mo/Te thin films are kept in a face-to-face manner inside the rapid thermal-processing furnace. The growth is carried out at a base pressure of 2 torr with a flow of 160 sccm of argon gas at different temperatures ranging from 400 °C to 700 °C. The x-ray diffraction peaks appear around 2 θ = 12.8°, 25.5°, 39.2°, and 53.2° corresponding to (002), (004), (006), and (008) orientation of a hexagonal 2H-MoTe2 structure. The characteristic Raman peaks of MoTe2, observed at ∼119 cm−1 and ∼172 cm−1, correspond to the in-plane E1g and out-of-plane A1g modes of MoTe2, whereas the prominent peaks of the in-plane E12g mode at ∼234 cm−1 and the out-of-plane B12g mode at ∼289 cm−1 are also observed. Root mean square (RMS) roughness is found to increase with increasing growth temperature. The bandgap of MoTe2 is calculated using a Tauc plot and is found to be 0.90 eV. Electrical characterizations are carried out using current–voltage and current–time measurement, where the maximum responsivity and detectivity are found to be 127.37 mA W−1 and 85.21 × 107 Jones for a growth temperature of 600 °C and an IR wavelength illumination of 1060 nm. [ABSTRACT FROM AUTHOR]

The pyroelectric effect has wide applications in various fields, such as infrared imaging, detection, alarms, and the expanding field of smart homes. The rapid advancement of smart systems, focusing on miniaturization and integration, requires pyroelectric infrared detectors with high pyroelectric coefficients and Curie temperatures to meet the requirements of integrated processes. However, the Curie temperature of commercial lead zirconate titanate is limited to <230°C, urgently looking for a breakthrough. Here, we explore pyroelectricity in Na0.5Bi4.5Ti4O15 (NBT) ceramics, characterized by a high Curie temperature (∼660°C). We systematically examined the crystal structure modifications and defect dipole effects of the Nb/Mn‐co‐doped NBT. The lattice expansion, distortion of the TiO6 octahedra, and structural transformation tendency from the orthorhombic to tetragonal phase facilitate dipole movements with increasing temperature. Furthermore, the Mn and Nb elements result in the formation of MnTi"–VO·· and NbTi·–MnTi" –NbTi· defect dipoles, inducing additional polarization changes in response to temperature variations. Finally, a significantly improved pyroelectric coefficient of 110 µC m2 K–1 and remarkable temperature stability from 25°C to 300°C is achieved in NBTM‐5Nb ceramics. This co‐doping strategy for enhancing pyroelectric performance can be expanded to other systems and substantially contribute to advancing high‐performance materials for infrared detection. [ABSTRACT FROM AUTHOR]

We demonstrate high-speed mid-wave infrared photoconductive detectors leveraging a lattice-mismatched, epitaxially grown InSb absorber material patterned with nanometer-scale hole arrays. We show that the nano-scale hole patterns allow for post-growth control over the detector response time by introducing recombination surfaces to increase non-radiative recombination. The photoconductive pixels are integrated into a microwave coplanar waveguide for high frequency characterization. The detector response is characterized as a function of temperature and hole-array dimensions. We show a detector response with characteristic time scales of tens of picoseconds and bandwidths up to 7 GHz at room temperature. The presented detectors offer a mechanism for engineering response times in long wavelength detectors for potential applications in high-speed sensing/imaging, free-space communication, ranging, or dual-comb spectroscopy. [ABSTRACT FROM AUTHOR]

Capacitance–voltage measurements are a powerful technique to determine doping profiles of semiconductor pn junctions and Schottky barrier diodes. The measurements were recently extended to III-V-based mid-wavelength nBn infrared detectors, and absorber doping densities have been extracted using the widely accepted Schottky approximation, where the potential drop across the device is assumed to be across the depleting absorber layer. However, this approach is limited to when the absorber region of the nBn is under high reverse bias and thus is only able to extract the absorber region doping profile. Here, we introduce a semi-analytical model that is capable of extracting barrier dopant polarity, doping concentration, and thickness, as well as contact and absorber layer doping concentrations, all from a capacitance–voltage measurement. Rather than solely considering the potential drop across the depleting layers, it considers the potential drop across the accumulating layer as well. This negative charge accumulation occurs for the contact and absorber layers in the case of reverse and forward biases, respectively. This allows for a single model to be applied to a capacitance–voltage curve at forward and reverse biases and it can provide regions of bias where the absorber transitions from depletion to accumulation. We compare the agreement of the semianalytical model with modeling results from commercially available finite element method software and experimental capacitance–voltage data. Finally, we show that the method is consistent with the Schottky approximation of extracting absorber doping densities at high reverse bias and discuss the model's limitations. [ABSTRACT FROM AUTHOR]

Pyroelectric infrared detectors (PIRDs) have a number of advantages over other IR sensors, including room-temperature operation, wide wavelength sensitivity, and low cost, leading to their use in many applications and a market expected to reach U.S.$68 million by 2025. Physical models that can be used to accurately predict the performances of PIRDs of different types are reviewed in detail. All polar dielectrics exhibit the pyroelectric effect, so there are many materials potentially available for use in PIRDs. Traditionally, a range of "figures-of-merit" (FoMs) are employed to aid the selection of the best material to use in a given application. These FoMs, and their utility in determining how a given pyroelectric material will behave in a PIRD, are reviewed in the light of the physical models and the availability of dielectric data, which cover the frequency ranges of greatest interest for PIRDs (0.1–100 Hz). The properties of several pyroelectric materials are reviewed, and models are derived for their dielectric properties as functions of frequency. It is concluded, first, that the availability of full-frequency dielectric data is highly desirable if accurate predictions of device performance are to be obtained from the models and that second, the FoMs have practical utility in only very limited circumstances. Thus, they must be used with considerable care and circumspection. The circumstances under which each FoM is likely to give a good prediction for utility are discussed. The properties of some recently researched pyroelectric materials, including lead-containing single crystals in the Pb[(Mg⅓Nb⅔)xTi1−x]O3 system and Na½Bi½TiO3–K½Bi½TiO3 based lead-free crystals and ceramics, are reviewed in the light of this, and their properties and potential for device applications compared with the industry-standard material, LiTaO3. It is concluded that while there is potential for significant device performance improvements by using improved materials, especially with the PMN-PT-based materials, factors such as temperature stability, uniformity, and ease-of-processing are at least as important as device performance in determining material utility. The properties reported for the new lead-free materials do not, as yet, promise a performance likely to compete with LiTaO3 for mm-scale detectors, a material that is both readily available and lead-free. [ABSTRACT FROM AUTHOR]

In this work, we study stimulated emission (SE) at 3–4 μm wavelengths from optically pumped bulk HgCdTe and HgTe/CdHgTe quantum-well heterostructures. It is proposed that, under intense excitation of such structures, energy relaxation of hot electrons occurs mostly via electron–hole scattering, while the relaxation of hot holes is direct, phonon-mediated. By balancing carrier generation/recombination and heating/cooling processes, we outline heat-induced limits to the operating temperatures of mid-IR HgCdTe lasers. Based on the existing experimental results for the SE around 3.5 μm, we predict that lasing at this wavelength may be achieved in 2.5 μm-pumped optical converters at temperatures as high as Tmax ∼ 270 K. [ABSTRACT FROM AUTHOR]

Abstract An object detection framework using thermal infrared (TIR) cameras is proposed to meet the needs of an advanced driver assistance system (ADAS) operating at night‐time and in low‐visibility conditions. The proposed detection framework, referred to as TIR‐YOLO‐ADAS, is an improvement of YOLOX for TIR object detection in ADAS. First, to address the disadvantages of TIR objects, the part of the attention mechanism is designed to enhance the discriminative ability of feature maps in the spatial and channel dimensions. Second, a focal loss function is used as the confidence loss function to enable the framework to focus on detection tasks of difficult, misclassified targets in the process of network training. The results of the ablation experiment on the Forward‐looking infrared (FLIR) thermal ADAS dataset indicate that the proposed framework significantly improves the performance of TIR object detection. Comparative experimental results further show that TIR‐YOLO‐ADAS performs favourably when compared with three representative detection algorithms. To evaluate the practicality and feasibility of the proposed framework in various applications, a qualitative assessment in real road scenarios was conducted. The experimental results confirm that the proposed framework performs promisingly and could be integrated into vehicle platforms as an ADAS module.

Free space optical communication with infrared light is a promising secure wireless optical communication technology, where infrared photodetectors are the core component. To date, such applications are based on epitaxial growth narrow‐band semiconductors facing the challenge of large‐area fabrication. Infrared colloidal quantum dots (CQDs) are of interest because of the high‐throughput solution processing. Here, large‐area CQD photodetectors with adjustable wavelengths covering 1.3–2.0 µm. For 1 × 1 mm2 CQD photodetector, the response time achieved within 1 µs at room temperature, responded sharply to the 25 kbps PRBS‐7 communication code is demonstrated. For 1.5 × 1.5 cm2 large‐area CQD photodetectors, a communication rate of 2 kbps is achieved. This work is a step toward the CQD application in the field of optical communications. [ABSTRACT FROM AUTHOR]

In the domain of high‐performance short‐wave infrared (SWIR) photodetection and imaging, existing technologies predominantly utilize single‐crystal germanium and III‐V semiconductors. Despite their efficacy, these materials are encumbered by laborious synthesis and complex fabrication demands. In this study, the synthesis of large‐area, high‐crystallinity Se0.2Te0.8 thin films through a CMOS‐compatible vacuum thermal evaporation process is reported. A high‐speed, broad‐spectrum photodetector engineered with an innovative Gr/Se0.2Te0.8/GaAs vertical heterostructure is presented, which capitalizes on the augmented carrier mobility and employs graphene innovatively as both a carrier collection interface and an electrode. This configuration facilitates a remarkably swift response time of 800 ns/1 µs at the crucial 1310 nm wavelength for optical communications. Moreover, the fabrication of a 5 × 5 array device demonstrates substantial SWIR imaging capabilities at ambient conditions, marking a paradigm shift in uncooled infrared imaging and communication technologies. This work not only extends the boundaries of SWIR photodetector performance but also underscores the potential of novel material systems in high‐speed optical applications. [ABSTRACT FROM AUTHOR]

Infrared images hold significant value in applications such as remote sensing and fire safety. However, infrared detectors often face the problem of high hardware costs, which limits their widespread use. Advancements in deep learning have spurred innovative approaches to image super-resolution (SR), but comparatively few efforts have been dedicated to the exploration of infrared images. To address this, we design the Residual Swin Transformer and Average Pooling Block (RSTAB) and propose the SwinAIR, which can effectively extract and fuse the diverse frequency features in infrared images and achieve superior SR reconstruction performance. By further integrating SwinAIR with U-Net, we propose the SwinAIR-GAN for real infrared image SR reconstruction. SwinAIR-GAN extends the degradation space to better simulate the degradation process of real infrared images. Additionally, it incorporates spectral normalization, dropout, and artifact discrimination loss to reduce the potential image artifacts. Qualitative and quantitative evaluations on various datasets confirm the effectiveness of our proposed method in reconstructing realistic textures and details of infrared images. [ABSTRACT FROM AUTHOR]

The electron correlations as triggered by on-site Coulomb repulsion within correlated vanadium dioxide (VO2) open up an emerging paradigm to explore new electronic phases and promising device applications. Apart from correlated electrical transport, the thermoelectric thermopower (S) of VO2 also undergoes abrupt variation across the critical temperature (TMIT) that sheds lights on the potential thermoelectric functionality. Nevertheless, bridging bi-functionality of VO2 associated with the thermistor and thermoelectric properties is still restricted by the limitation in improving the absolute magnitude of S and temperature coefficient of resistance (TCR). Herein, we demonstrate the widely adjustable metal–insulator transition (MIT) behavior and overlooked thermoelectric performance for Ti-substituted VO2 pellets that enable the bi-functionality strategy as combined with thermistor and thermoelectric properties. As-achieved tunable TMIT while maintaining large |TCR| is herein achieved for Ti-substituted VO2 pellets that enables practical device applications near room temperature. Apart from the well-known MIT functionality, we reveal the overlooked thermoelectric properties for VO2 via coherently co-sintering with TiO2 that introduces a new freedom (thermopower). Specifically, the largely enhanced thermopower observed for insulating V1−xTixO2 exceeds the one for pristine VO2 by five times, while the thermoelectric power factor for its metallic phase is comparable to typical organic or oxide thermoelectric materials. The presently achieved thermistor and thermoelectric bi-functionality (e.g., |S| > 100 μV/K and |TCR| > 1 K−1) for Ti-substituted VO2 pellets extends the horizons in material designs that combines such a bi-functionality to achieve both the passive and active sensing for improving the accuracy in thermal perturbations of VO2 bulk as infrared detectors near room temperature. [ABSTRACT FROM AUTHOR]

Silicon (Si)‐based photodetectors are cost‐effective, eco‐friendly, and compatible with on‐chip complementary metal‐oxide‐semiconductor (CMOS) technology. However, expanding their photoresponse into the short‐wavelength‐infrared region beyond 1.1 µm remains challenging because of the intrinsic bandgap of Si. In this study, an ion implantation sulfur‐doped Si‐based infrared photodetector featuring a blocked impurity band (BIB) structure is investigated. The detector achieves an extended sub‐bandgap infrared response up to 2 µm through impurity band transitions, facilitated by the artificial creation of a deep‐level impurity band within the Si bandgap. The device exhibited a competitive photodetection effect with a high responsivity of 107.3 mA W−1 and an external quantum efficiency of 10.2%. Notably, the detector yielded an enhanced response speed with a raising time of 46 µs and a decay time of 135 µs at 1310 nm under room temperature. Finally, the versatile applications of this detector is presented in a multitude of scenarios encompassing material composition identification, multi‐band imaging, and optical communication. The proposed investigation not only proposed a method for Si‐based infrared detectors but also constituted a contribution to the advancement of silicon photonics. [ABSTRACT FROM AUTHOR]

Cutting-edge mid-wavelength infrared (MWIR) sensing technologies leverage infrared photodetectors, memory units, and computing units to enhance machine vision. Real-time processing and decision-making challenges emerge with the increasing number of intelligent pixels. However, current operations are limited to in-sensor computing capabilities for near-infrared technology, and high-performance MWIR detectors for multi-state switching functions are lacking. Here, we demonstrate a non-volatile MoS2/black phosphorus (BP) heterojunction MWIR photovoltaic detector featuring a semi-floating gate structure design, integrating near- to mid-infrared photodetection, memory and computing (PMC) functionalities. The PMC device exhibits the property of being able to store a stable responsivity, which varies linearly with the stored conductance state. Significantly, device weights (stable responsivity) can be programmed with power consumption as low as 1.8 fJ, and the blackbody peak responsivity can reach 1.68 A/W for the MWIR band. In the simulation of Faster Region with convolution neural network (CNN) based on the FLIR dataset, the PMC hardware responsivity weights can reach 89% mean Average Precision index of the feature extraction network software weights. This MWIR photovoltaic detector, with its versatile functionalities, holds significant promise for applications in advanced infrared object detection and recognition systems. In-sensor computing architectures can provide energy-efficient multifunctional capabilities, but their application to the mid-infrared range is challenging. Here, the authors report the realization of non-volatile MoS2/black phosphorus photovoltaic detectors, integrating near- to mid-infrared photodetection, memory and computing functionalities. [ABSTRACT FROM AUTHOR]

This Letter details a pioneering study on the design and nanofabrication process of a thermoelectric infrared radiation detector using a suspended polyimide membrane. The research includes a comprehensive analysis of thermoelectric doped Bi2Te3 thin films, comparing their expected performance regarding noise and specific detectivity with other infrared detectors, particularly those in the silicon sector. Experimental results and calculations shed light on responsivity and time constants. In the absence of absorption layers, specific detectivity values for visible and near infrared radiation are measured at 9.2 × 107 and 2.9 × 107 cm Hz / W , respectively, with a time constant nearing 20 ms. Calculations show that introducing an optimized absorption layer with ε = 1 significantly improves specific detectivity, reaching 9.0 × 108 cm Hz / W. Subsequent calculations also show that further enhancement can be obtained by etching the polyimide membrane to a 1-micron thickness, resulting in an exceptional specific detectivity value of 8.4 × 109 cm Hz / W , placing it among the best in the current state-of-the-art. [ABSTRACT FROM AUTHOR]

As the weak link in electro-optical imaging systems, photodetectors have always faced the threat of laser damage. In this paper, we experimentally investigated the damage mechanism of the photodetector induced by the out-of-band laser. The damage thresholds of the mid-infrared pulsed laser for Charge Coupled Device (CCD) and HgCdTe detectors were determined through damage experiments. The analysis of the damage phenomena and data for both CCD and HgCdTe detectors clearly demonstrated that out-of-band mid-infrared pulsed lasers could entirely incapacitate CCD and HgCdTe detectors. Our analysis of the damage process and data revealed that the primary mechanism of damage to CCD and HgCdTe detectors by mid-infrared pulsed lasers was primarily thermal. This study serves as a reference for further research on the mid-infrared pulsed laser damage mechanisms of CCD and HgCdTe detectors, as well as for laser protection and performance optimization in imaging systems. [ABSTRACT FROM AUTHOR]

Multiband infrared photodetectors (PDs) have garnered considerable attention due to their potential in various fields such as biomedical applications, optical communications, and military operations. However, the lattice mismatch of mature bulk semiconductors with varying bandgaps in the same PD pixel has impeded the advancement of multiband infrared detectors. Colloidal quantum dots (CQDs), with adjustable bandgaps, wide spectral range, and easy solution processing are promising materials for the fabrication of multiband infrared detectors. Herein, HgTe CQDs are used with varying bandgaps to construct a three‐band infrared detector with short‐wave infrared of 1.7 and 2.4 μm and midwave infrared of 4 μm. The utilization of Ag2Te nanocrystals to bring in spatially stable doping is the key to achieving three‐band infrared detectors. Through adjusting bias polarity, the detectors switch between a three‐band mode and a dual‐band mode. The detector exhibits exceptional detection performance, with detectivity above 3 × 1010 Jones in three‐band mode. [ABSTRACT FROM AUTHOR]

The B-BOP detector is composed of polarization sensitive bolometer arrays in the 70–350 µm spectral range with a goal sensitivity around one attoWatt/sqrt (Hz). A polarized infrared calibration set-up is required to evaluate its performances. The calibration source is based on 6-ring-shaped, concentric blackbody-like emitters that can be individually controlled. The total emitting surface is therefore tunable from 9 up to 1200 mm2. The temperature is tunable from 1 to 40 K without disturbing the dilution cryostat and the working temperature of the detector arrays. The present paper describes the source, the rotating polarizer at low temperature, the modulation means, and the complete optical tube leading polarized infrared photons for characterizing detectors down to femtowatt level. Details of the design and realization are discussed. [ABSTRACT FROM AUTHOR]

The Balloon Experiment for Galactic INfrared Science (BEGINS) is a concept for a sub-orbital observatory that will operate from λ = 25 to 250 μ m to characterize dust in the vicinity of high-mass stars. The mission's sensitivity requirements will be met by utilizing arrays of 1840 lens-coupled, lumped-element kinetic inductance detectors (KIDs) operating at 300 mK. Each KID will consist of a titanium nitride (TiN) parallel strip absorbing inductive section and parallel plate capacitor deposited on a Silicon (Si) substrate. The parallel plate capacitor geometry allows for reduction of the pixel spacing. At the BEGINS focal plane, the detectors require optical NEPs from 2 × 10 - 16 to 6 × 10 - 17 W/ Hz from 25 to 250 μ m for optical loads ranging from 4 to 10 pW. We present the design, optical performance and quasiparticle lifetime measurements of a prototype BEGINS KID array at 25 μ m when coupled to Fresnel zone plate lenses. For our optical set up and the absorption efficiency of the KIDs, the electrical NEP requirement at 25 μ m is 7.6 × 10 - 17 W/ Hz for an absorbed optical power of 0.36 pW. We find that over an average of five resonators the the detectors are photon noise limited down to about 200 fW, with a limiting NEP of about 7.4 × 10 - 17 W/ Hz . Future arrays will be coupled to microlens arrays and have higher optical efficiencies. [ABSTRACT FROM AUTHOR]

Nonlinear optical rectification (NOR) coefficients in symmetric double-graded quantum wells with different geometrical configurations under non-resonant laser field in the presence of electric and magnetic fields are theoretically investigated. The quantum states under the applied external fields are obtained under effective mass approximation and using diagonalization method. Our calculated results indicate that the above-mentioned external fields play a significant role in manipulating the resonant peak values and peak positions of nonlinear optical rectification coefficients of the quantum system dynamically. Considerable NOR coefficient can be achieved, not only by choosing appropriate laser dressing parameter as well as the electric and magnetic fields, but also by choosing appropriate well and barrier widths. Our results show great advantages in dynamically tuning NOR coefficient of symmetric double-graded quantum wells using multi-physic fields, paving the way for possible application for tunable infrared detector and signal processing based on symmetric double-graded quantum wells. [ABSTRACT FROM AUTHOR]

GeSn has attracted increasing attention due to its tunable bandgap from indirect to direct resulting in unique electronic and optoelectronic capabilities. Chemical vapor deposition (CVD) is well acknowledged as an advanced growth method for GeSn, demonstrating its capability with grown materials for infrared lasers and detector development. As an in situ diagnostics of the CVD process, a residual gas analyzer (RGA) could enable the detection of all gaseous species during growth, thus probing the growth dynamics and mechanism. Therefore, it is highly desirable but is lacking in the (Si)GeSn research community. This work utilized an RGA equipped with a specialized differential vacuum pumping system to analyze the mass spectra of the GeSn CVD precursors of SnCl4, GeH4, and their combination. The spectra of SnCl4 collected from gas samples at a standard base pressure of 0.3 Torr display consistent fragments with central mass-to-charge ratios (m/z) of 78, 120, 155, 225, and 260, corresponding to Sn+, SnCl2+, SnCl+, SnCl2+, SnCl3+, and SnCl4+, respectively. These profiles closely resemble those observed in the National Institute of Standards and Technology and Wiley and Matsumoto et al. The simultaneous introduction of SnCl4 and GeH4 at a combined pressure of several tens of Torr yields spectra, indicating a chemical reaction that produces GeCl4 at room temperature in the vacuum chamber and tubing. Utilizing Gaussian16 and ORCA codes, the ab initio and density functional thermochemistry computations were employed to predict potential essential reactions and validate the experimental findings. [ABSTRACT FROM AUTHOR]

High-quality III–V quantum structures, advanced epitaxial technologies, and characterization methods are essential to drive the development of infrared optoelectronic materials and devices. As an important component of type II superlattices, InAs/InxGa1−xAsySb1−y would play an important role in the field of high-performance infrared detectors due to their excellent luminescence efficiency and high crystal quality. However, their interfacial characteristics and the associated minority carrier lifetime are still difficult to identify. In this paper, an atomic imaging technique was used to identify the arrangement and distribution of elements of the InAs/In0.5Ga0.5As0.5Sb0.5 superlattice. Our results confirm the epitaxy mechanism that the quaternary alloy consists of two kinds of ternary alloy in one monolayer. Moreover, by separating the cation and anion columns in the elementally resolved atomic images of the InAs/In0.5Ga0.5As0.5Sb0.5 superlattice, we demonstrate that the interfacial atomic intermixing is less than one molecular layer thickness. Therefore, benefiting from excellent interface quality, InAs/In0.5Ga0.5As0.5Sb0.5 superlattice exhibited high radiation recombination efficiency in the long-wave infrared band (∼8.5 μm), and longer minority carrier lifetime (∼810 ns at 90 K). [ABSTRACT FROM AUTHOR]

We demonstrate a quantum ratchet detector, which is a high-resistance photovoltaic mid-infrared detector based on an engineered spatial arrangement of subbands. In photovoltaic quantum-well photodetectors, in which unidirectional photocurrent is generated by asymmetric quantum-well structures, maximization of device resistance by suppressing undesired electron transports is crucial for minimizing noise. A semi-quantitative guideline suggests the significance of spatial separation between wavefunctions for reducing the conductance from the ground state. Here, we employ a step quantum well made of a shallow floor and a deep well. Photoexcited electrons are quickly transferred to a separated location from the ground state through fast resonant tunneling and phonon scattering, and then they are allowed to flow in only one direction. This architecture is made possible by the use of a GaAs/AlGaAs material system, and it achieves a resistance as high as 6.0 × 104 Ωcm2 with a single-period structure. Combined with optical patch antennas for responsivity enhancement, we demonstrate a maximum background-limited specific detectivity of 6.8 × 1010 cmHz1/2/W at 6.4 μm, 77 K for normal incidence, and a background-limited-infrared-photodetector temperature of 98 K. [ABSTRACT FROM AUTHOR]

Deep defects in the long-wave infrared (LWIR) HgCdTe heterostructure photodiode were measured via deep-level transient spectroscopy (DLTS) and photoluminescence (PL). The n+-P+-π-N+ photodiode structure was grown by following the metal–organic chemical vapor deposition (MOCVD) technique on a GaAs substrate. DLTS has revealed two defects: one electron trap with an activation energy value of 252 meV below the conduction band edge, located in the low n-type-doped transient layer at the π-N+ interface, and a second hole trap with an activation energy value of 89 meV above the valence band edge, located in the π absorber. The latter was interpreted as an isolated point defect, most probably associated with mercury vacancies (VHg). Numerical calculations applied to the experimental data showed that this VHg hole trap is the main cause of increased dark currents in the LWIR photodiode. The determined specific parameters of this trap were the capture cross-section for the holes of σp = 10−16–4 × 10−15 cm2 and the trap concentration of NT = 3–4 × 1014 cm−3. PL measurements confirmed that the trap lies approximately 83–89 meV above the valence band edge and its location. [ABSTRACT FROM AUTHOR]