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This paper presents a theoretical analysis of an nBp infrared barrier detector's performance intended to operate at a room temperature (300 K) based on AIIIBV materials—In1-xGaxAsySb1−y quaternary compound—lattice-matched to the GaSb substrate with a p-n heterojunction ternary Al1−xGaxSb barrier. Numerical simulations were performed using a commercial Crosslight Software—package APSYS. The band structure of the nBp detector and the electric field distribution for the p-n heterojunction with and without a potential barrier were determined. The influence of the barrier-doping level on the detector parameters was analyzed. It was shown that Shockley-Read-Hall (SRH) recombination plays a decisive role in carrier transport for lifetimes shorter than 100 ns. The influence of the absorber/barrier thickness on the detector's dark current density and photocurrent was investigated. It was shown that valence band offset does not influence the device's performance. The quantum efficiency reaches its maximum value for an absorber's thickness of ~3 μm. The performed simulations confirmed the possibility of the detector's fabrication exhibiting high performance at room temperature based on quaternary compounds of AIIIBV materials for the short wavelength infrared range. [ABSTRACT FROM AUTHOR]

The influence of the etching method on the occurrence of defect levels in InAs/InAsSb type-II superlattice (T2SLs) and MCT photodiode is presented. For both analyzed detectors, the etching process was performed by two methods: wet chemical etching and dry etching using an ion beam (RIE—reactive ion etching). The deep-level transient spectroscopy (DLTS) method was used to determine the defect levels occurring in the analyzed structures. The obtained results indicate that the choice of etching method affects the occurrence of additional defect levels in the MCT material, but it has no significance for InAs/InAsSb T2SLs. [ABSTRACT FROM AUTHOR]

In the last twenty years, nanofabrication progress has allowed for the emergence of a new photodetector family, generally called low-dimensional solids (LDSs), among which the most important are two-dimensional (2D) materials, perovskites, and nanowires/quantum dots. They operate in a wide wavelength range from ultraviolet to far-infrared. Current research indicates remarkable advances in increasing the performance of this new generation of photodetectors. The published performance at room temperature is even better than reported for typical photodetectors. Several articles demonstrate detectivity outperforming physical boundaries driven by background radiation and signal fluctuations. This study attempts to explain these peculiarities. In order to achieve this goal, we first clarify the fundamental differences in the photoelectric effects of the new generation of photodetectors compared to the standard designs dominating the commercial market. Photodetectors made of 2D transition metal dichalcogenides (TMDs), quantum dots, topological insulators, and perovskites are mainly considered. Their performance is compared with the fundamental limits estimated by the signal fluctuation limit (in the ultraviolet region) and the background radiation limit (in the infrared region). In the latter case, Law 19 dedicated to HgCdTe photodiodes is used as a standard reference benchmark. The causes for the performance overestimate of the different types of LDS detectors are also explained. Finally, an attempt is made to determine their place in the global market in the long term. [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]

Perovskites have been largely implemented into optoelectronics as they provide several advantages such as long carrier diffusion length, high absorption coefficient, high carrier mobility, shallow defect levels and finally, high crystal quality. The brisk technological development of perovskite devices is connected to their relative simplicity, high-efficiency processing and low production cost. Significant improvement has been made in the detection performance and the photodetectors' design, especially operating in the visible (VIS) and near-infrared (NIR) regions. This paper attempts to determine the importance of those devices in the broad group of standard VIS and NIR detectors. The paper evaluates the most important parameters of perovskite detectors, including current responsivity (R), detectivity (D*) and response time (τ), compared to the standard photodiodes (PDs) available on the commercial market. The conclusions presented in this work are based on an analysis of the reported data in the vast pieces of literature. A large discrepancy is observed in the demonstrated R and D*, which may be due to two reasons: immature device technology and erroneous D* estimates. The published performance at room temperature is even higher than that reported for typical detectors. The utmost D* for perovskite detectors is three to four orders of magnitude higher than commercially available VIS PDs. Some papers report a D* close to the physical limit defined by signal fluctuations and background radiation. However, it is likely that this performance is overestimated. Finally, the paper concludes with an attempt to determine the progress of perovskite optoelectronic devices in the future. [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]

The performance of long-wave infrared (LWIR) = 0.22 HgCdTe avalanche photodiodes (APDs) was presented. The dark currentvoltage characteristics at temperatures 200 K, 230 K, and 300 K were measured and numerically simulated. Theoretical modeling was performed by the numerical Apsys platform (Crosslight). The effects of the tunneling currents and impact ionization in HgCdTe APDs were calculated. Dark currents exhibit peculiar features which were observed experimentally. The proper agreement between the theoretical and experimental characteristics allowed the determination that the material parameters of the absorber were reached. The effect of the multiplication layer profile on the detector characteristics was observed but was found to be insignificant. [ABSTRACT FROM AUTHOR]

HgCdTe is a well-known material for state-of-the-art infrared photodetectors. The interd-iffused multilayer process (IMP) is used for Metal–Organic Chemical Vapor Deposition (MOCVD) of HgCdTe heterostructures, enabling precise control of composition. In this method, alternating HgTe and CdTe layers are deposited, and they homogenize during growth due to interdiffusion, resulting in a near-uniform material. However, the relatively low (350 °C) IMP MOCVD growth temperature may result in significant residual compositional inhomogeneities. In this work, we have investigated the residual inhomogeneities in the IMP-grown HgCdTe layers and their influence on material properties. Significant IMP growth-related oscillations of composition have been revealed in as-grown epilayers with the use of a high-resolution Secondary Ion Mass Spectroscopy (SIMS). The oscillations can be minimized with post-growth annealing of the layers at a temperature exceeding that of growth. The electric and photoelectric characterizations showed a significant reduction in the background doping and an increase in the recombination time, which resulted in dramatic improvement of the spectral responsivity of photoconductors. [ABSTRACT FROM AUTHOR]

The paper reports on a long-wave infrared (cut-off wavelength ~ 9 μm) HgCdTe detector operating under nbiased condition and room temperature (300 K) for both short response time and high detectivity operation. The ptimal structure in terms of the response time and detectivity versus device architecture was shown. The response time of the long-wave (active layer Cd composition, xCd = 0.19) HgCdTe detector for 300 K was calculated at a level of τs ~ 1 ns for zero bias condition, while the detectivity − at a level of D* ~ 109 cmHz1/2/W assuming immersion. It was presented that parameters of the active layer and P+ barrier layer play a critical role in order to reach τs ≤ 1 ns. An extra series resistance related to the processing (RS+ in a range 5−10 Ω) increased the response time more than two times (τs ~ 2.3 ns).

In this work we report simulation and experimental results for an MWIR HgCdTe photodetector designed by computer simulation and fabricated in a joint laboratory run by VIGO Sytems S.A. and Military University of Technology. The device is based on a modified N+pP+ heterostructure grown on 2”., epiready, semi-insulating (100) GaAs substrates in a horizontal MOCVD AIX 200 reactor.

A method for defects extraction for a mercury cadmium telluride (MCT) multilayer lowbandgap heterostructure is presented. The N+/T/p/T/P+/n+ epitaxial layer was deposited on a GaAs substrate by a metal-organic chemical vapour deposition (MOCVD). The absorber was optimized for a cut-off wavelength of λc= 6 µm at 230 K. Deep-level transient spectroscopy (DLTS) measurements were conducted for the isolated junctions of the N+/T/p/T/P+/n+ heterostructure. Three localised point defects were extracted within the ptype active layer. Two of them were identified as electron traps and one as a hole trap, respectively. [ABSTRACT FROM AUTHOR]

Recently, there has been significant interest in type-II superlattice (T2SL) infrared detectors based on both InAs/GaSb and InAs/InAsSb material systems, and fully operating devices have been presented in the mid- (MWIR) and long-wavelength (LWIR) infrared ranges. In addition, theoretical simulations and experimental reports show high-performance T2SL devices in the very-long-wavelength infrared range (VLWIR) (cutoff wavelength, λc ≥ 12 μm). Devices in this wavelength range are essential for space-based applications. In VLWIR, the existing detectors with satisfactory performance are extrinsic silicon detectors operating under heavy, bulky and short-lifetime multistage cryocoolers. These disadvantages are mainly critical for space applications, and thus, developing a device exhibiting a higher operating temperature (HOT) is of high priority. We report on a photoconductive T2SL InAs/InAsSb detector with λc > 18 μm (limited by a GaAs substrate) and high-operating-temperature (HOT) conditions (T = 210–240 K) grown on thick semi-insulating GaA substrates by molecular beam epitaxy (MBE). [ABSTRACT FROM AUTHOR]

Localization landscape (LL) theory is applied to directly model carrier transport in a type II superlattice (T2SL) InAs/InAsSb photoconductor system. It is difficult to apply the classical Poisson and drift–diffusion (DD) model to direct modeling of carrier transport in superlattice systems because quantum effects need to be considered. With the LL theory, it is possible to obtain the effective quantum potential seen by carriers. By coupling the LL theory with the Poisson–DD model and replacing the traditional conduction and valence potentials with effective quantum potentials, it is possible to directly model carrier transport in a T2SL system. We compare the results of this approach with experimental results and find very good agreement, which indicates that this method will provide an efficient tool for the T2SL design. [ABSTRACT FROM AUTHOR]

The 17th International Workshop on Advanced Infrared Technology and Applications (AITA 2023) was held in Venice, Italy from 10-13 September 2023. The conference, which has been running since 1992, aims to assess the state of the art of infrared technology and present its applications. The event was organized by various institutions and received patronage from two organizations. The technical program included sessions on topics such as non-destructive testing, sensors, image processing, remote sensing, and biomedical applications. A plenary lecture was given on the role of light in infrared astronomy. The conference also featured the sixth Under 35 Best Paper Award, which was given to three authors for their contributions. The event received support from Teledyne FLIR and Telops. The 18th edition of AITA is scheduled to take place in Kobe, Japan in 2025. [Extracted from the article]

The dual-band avalanche photodiode (APD) detector based on a HgCdTe material system was designed and analysed in detail numerically. A theoretical analysis of the two-colour APD intended for the mid wavelength infrared (MWIR) and long wavelength infrared (LWIR) ranges was conducted. The main purpose of the work was to indicate an approach to select APD structure parameters to achieve the best performance at high operating temperatures (HOT). The numerical simulations were performed by Crosslight numerical APSYS platform which is designed to simulate semiconductor optoelectronic devices. The current-voltage characteristics, current gain, and excess noise analysis at temperature T = 230 K vs. applied voltage for MWIR (U = 15 V) and LWIR (U = -6 V) ranges were performed. The influence of low and high doping in both active layers and barrier on the current gain and excess noise is shown. It was presented that an increase of the APD active layer doping leads to an increase in the photocurrent gain in the LWIR detector and a decrease in the MWIR device. The dark current and photocurrent gains were compared. Photocurrent gain is higher in both spectral ranges. [ABSTRACT FROM AUTHOR]