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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]

A3B5 materials used for the superlattice (SL) fabrication have properties that enable the design of devices optimized for infrared (IR) detection. These devices are used in the military, industry, medicine and in other areas of science and technology. The paper presents the theoretical assessment and analysis of the InAs/InAs1−xSbx type-II superlattice (T2SL) (grown on GaSb buffer layer) strain impact on the bandgap energy and on the effective masses of electrons and holes at 150 K. The theoretical research was carried out with the use of the commercial program SimuApsys (Crosslight). The k·p method was adopted in T2SL modeling. Luttinger coefficients (γ1, γ2 and γ3) were assessed assuming the Kane coefficient F = 0. The bandgap energy of ternary materials (InAsxSb1−x) was determined assuming that the bowing parameter (bg) for the above-mentioned temperature is bg = 750 meV. The cutoff wavelength values were estimated based on the theoretically determined absorption coefficients (from approximation the quadratic absorption coefficient). The bandgap energy was calculated according to the following formula: Eg = 1.24/λcutoff. The theoretical simulations allowed us to conclude that the strain in T2SL causes the Eg shift, which also has an impact on the effective masses me and mh, playing an important role for the device's optical and electrical performance. The T2SLs-simulated results at 150 K are comparable to those measured experimentally. [ABSTRACT FROM AUTHOR]

Highlights • Selection of the d 1 determines the N S , at which detectivity reaches maximum. • d 1opt is higher for equal- than for matched-absorbers detectors. • D* MAX is slightly lower for equal- than for matched-absorbers detectors. • Detectivities are comparable for both type of interband cascade detectors. • Total absorber thickness is higher for the matched-absorbers detector. Abstract The paper presents the performance of the interband cascade type-II superlattice infrared photodetectors. Such photodetectors are made up of multiple stages, which are connected in series using an interband tunneling heterostructure. In this paper, we compare two different architectures of the cascade structure: equal absorber thickness in all stages and varied absorber thickness. In our calculation, in the case of equal absorber throughout the structure, we took into account electrical current gain. The selection of the first absorber thickness d 1 determines the number of possible stages N S , at which detectivity reaches maximum value, which is especially important in case of varied absorbers thickness to meet the quantum efficiency condition (equal quantum efficiency in each stage of the device). Optimal first absorber thickness d 1opt is higher for equal absorbers than for matched-absorbers detectors, but maximum value of detectivity is slightly lower. We compared theoretical results with experimental ones, obtaining good agreement. [ABSTRACT FROM AUTHOR]

Four types of barrier detectors based on a type II InAs/InAsSb superlattice with a wide-gap barrier made of a solid AlInAsSb lattice matched to the GaSb buffer were compared. The tested detectors differed in the type of doping of the active layer and the level and type of doping of the contact layer at the barrier. The epitaxial layers were deposited on GaAs (100) substrates using the molecular beam epitaxy method. The spectral and current–voltage characteristics of the analyzed detectors were compared. The highest current responsivities were observed in the structure with a p-type absorber (p+BpN+). Detectors with an n-type absorber (p+Bnn+, n+Bnn+, and nBnn+) show an increase in the current responsivity with an increase in the reverse bias voltage due to the reduction in the undesirable barrier in the valence band. Arrhenius characteristics for the dark current show that only in nBnn+ detectors, it was possible to limit the generation–recombination current. These detectors at 150 K were characterized by the highest normalized detectivity of approximately 3 × 1011 cm · Hz1/2/W. The obtained results were compared with literature data, showing that the parameters of type II superlattice photodetectors are close to those of HgCdTe photodiodes according to the "Rule 07" and "Rule 22" principles. [ABSTRACT FROM AUTHOR]

This paper presents a thorough analysis of the current–voltage characteristics of uncooled HgCdTe detectors optimized for different spectral ranges. HgCdTe heterostructures were grown by means of metal–organic chemical vapor deposition (MOCVD) on GaAs substrates. The obtained detector structures were measured using a Keysight B1500A semiconductor device analyser controlled via LabVIEW for automation. The experimental characteristics were compared with numerical calculations performed using the commercial platform SimuAPSYS (Crosslight). SimuAPSYS supports detector design and allows one to understand different mechanisms occurring in the analysed structures. The dark current density experimental data were compared with theoretical results at a temperature of 300 K for short, medium, and long wavelength infrared ranges. The dark current density of detectors optimized for different wavelengths was determined using various generation–recombination mechanisms. Proper matching between experimental and theoretical data was obtained by shifting the Shockley–Read–Hall carrier lifetime and the Auger–1 and Auger–7 recombination rates. Exemplary spectral responses were also discussed, giving a better insight into detector performance. The matching level was proven with a theoretical evaluation of the zero-bias dynamic resistance–area product (R0A) and the current responsivity of the designed detectors. [ABSTRACT FROM AUTHOR]

In the last two decades an implementation of barrier detectors considerably strengthen the position of InAsSb-based bulk and superlattice structures in infrared detector family. In spite of fact that the dependence of InAs 1−x Sb x energy gap (E g) on Sb, x -composition and temperature, T , has been experimentally investigated by many research groups since 1964, its E g (x , T) dependence is not precisely evaluated. An uncertainty in E g (x , T) value has detrimental influence on the intrinsic carrier concentration estimate. This paper attempts to critically assess the relevant literature data on this topic. The paper presents theoretical analysis of the bowing parameter influence on the energy gap and intrinsic carrier concentration versus the Sb molar composition and temperature. The calculations are carried out for temperature range 100–300 K. The obtained results differ significantly from ones used so far, especially in the low temperatures range having important implications on the InAsSb material properties and device performance. The proper correlation between theoretical predictions and experimental data has been reached only in the range of higher temperatures (above 200 K). [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]

The detectivity characteristics of interband cascade infrared type-II superlattice detectors for long-wave infrared detection (λcut-off = 8 μm at room temperature) are discussed. We present comparison of two superlattices: InAs/GaSb and InAs/InAsSb, assuming the characteristic parameters—absorption coefficients α and carrier lifetimes τ published in literature. Dependence of the Johnson-noise limited detectivity on the absorber thickness for a different number of stages is reported. Higher detectivity D* value can be achieved by increasing the carrier lifetime. However, for detectors based on type-II InAs/GaSb superlattice increasing the carrier lifetime up to 25 ns leads to a situation in which one stage is preferred, i.e. for detector with a single absorber, we obtain the highest detectivity value. In the case of InAs/InAsSb material, the situation is similar for τ ≥ 80 ns. We have shown that the optimal absorber thickness at which the highest detectivity values are obtained depends not only on the absorption coefficient α and the number of stages NS, but also on the carrier diffusion length L. According to a calculations, cascade detectors based on Ga-free material should have much higher optimal absorber thicknesses than materials based on InAs/GaSb. [ABSTRACT FROM AUTHOR]

This study reports on photoelectrical performance of the long‐wave infrared HgCdTe high operating temperature (200–230 K) detector for the fast response time operating under unbiased conditions. The detailed analysis of the response time as a function of device architecture was conducted pointing out optimal working conditions and structure. The response time of the long‐wave (xCd = 0.19) HgCdTe detector for temperatures reached by thermoelectrical cooling (200–230 K) was estimated at the level of τs < 0.6 ns for unbiased condition while responsivity Ri ∼ 1.8 A/W and detectivity was assessed at the level of D* ∼ 1.6 × 1010 cm Hz1/2 /W. It was shown that extra series resistance Rseries < 10 Ω (resistance–capacitance time constant) plays a decisive role in order to reach τs < 1 ns meaning that device processing is much more important rather than fundamental limitations imposed by physics. [ABSTRACT FROM AUTHOR]

This study reports on photoelectrical performance of the long-wave infrared HgCdTe high operating temperature (200-230 K) detector for the fast response time operating under unbiased conditions. The detailed analysis of the response time as a function of device architecture was conducted pointing out optimal working conditions and structure. The response time of the long-wave (xCd = 0.19) HgCdTe detector for temperatures reached by thermoelectrical cooling (200-230 K) was estimated at the level of τs < 0.6 ns for unbiased condition while responsivity Ri ~ 1.8 A/W and detectivity was assessed at the level of D* ~ 1.6 × 1010 cm Hz½/W. It was shown that extra series resistance Rseries < 10 Ω (resistance-capacitance time constant) plays a decisive role in order to reach τs < 1 ns meaning that device processing is much more important rather than fundamental limitations imposed by physics. [ABSTRACT FROM AUTHOR]

We investigate the high-operating temperature performance of InAsSb/AlSb heterostructure detectors with cutoff wavelengths near 5 μm at 230 K. The devices have been fabricated with different types of absorbing layers: nominally undoped absorber (with n-type conductivity), and both n- and p-type doped. The results show that the device performance strongly depends on absorber layer type. Generally, the p-type absorber provides higher values of current responsivity than the n-type absorber, but at the same time also higher values of dark current. The device with the nominally undoped absorbing layer shows moderate values of both current responsivity and dark current. Resulting detectivities D* of nonimmersed devices vary from 2 × 109 to 5 × 109 cmHz1/2W-1 at 230 K, which is easily achievable with a two-stage thermoelectric cooler. Optical immersion increases the detectivity up to 5 × 1010 cmHz1/2W-1. [ABSTRACT FROM AUTHOR]

The paper reports on a long-wave infrared (cut-off wavelength ~ 9 µm) HgCdTe detector operating under unbiased condition and room temperature (300 K) for both short response time and high detectivity operation. The optimal 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). [ABSTRACT FROM AUTHOR]

Theoretical and experimental investigations on the response time improvement of unbiased longwave infrared (LWIR) HgCdTe detectors operating at temperatures T = 230 K were presented. Metal–organic chemical vapor deposition technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition and donor/acceptor doping and without postgrown ex-situ annealing. The time constant is lower in biased detectors due to Auger-suppression phenomena and reduction of diffusion capacitance related to a wider depletion region. The relatively high bias current requirements and excessive low-frequency noise, which reduces the detectivity of biased detectors, inspire research on the time constant improvement of unbiased detectors. The response time of high-operating temperature LWIR HgCdTe detectors revealed complex behavior being dependent on the applied reverse bias, the operating temperature, the absorber thickness and doping, the series resistance, and the electrical area of the devices. The response time of 2 ns was achieved for unbiased 30 × 30 μm HgCdTe structures with λ50% = 10.6 μm operating at T = 230 K. [ABSTRACT FROM AUTHOR]