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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]

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]

This paper presents a response time/time constant of III-V material-based interband long wavelength multistage infrared detector optimized for a wavelength of 10.6 µm at 200 K. The device is based on the InAs/InAsSb type-II superlattice with highly doped p+/n+ tunneling junctions among the stages. The detector exhibits a response time of 9.87 ns under zero voltage condition, while for 0.15 V reverse bias, that time decreases to approximately 350 ps. The presented device shows a significant increase in response time, especially for low bias, and for a voltage of −0.2 V, the decrease in the detector's response time by an order of magnitude was estimated. Higher voltage slightly affects the time constant, and between −0.3 V and −1 V, it varies between 300 and 400 ps. The significant change in the detector's response time between −0.1 V and −0.2 V probably results from electric field drop over entire absorber region. The optimal operating condition can be reached for −0.15 V, where the time constant reaches approximately 350 ns with peak detectivity at a level of ~3 × 109 Jones. [ABSTRACT FROM AUTHOR]

This paper presents the performance of an interband cascade long-wavelength infrared detector designed for high operating temperatures supported by immersion lenses. The device is based on the "Ga-free" InAs/InAsSb type-II superlattice with highly doped p+/n+ superlattice tunneling junctions connecting adjacent stages. Detectivity of the multi-junction heterostructure detector exceeding 1010 cm Hz1/2/W was estimated at wavelength λ ~ 9 µm and T = 210 K and ~ 3 × 108 cm Hz1/2/W for T = 300 K, achieving a tenfold improvement in detectivity in comparison to a device without an immersion lens and 30-fold improvement in detectivity in comparison to the single-stage device. [ABSTRACT FROM AUTHOR]

This letter presents InAs $/$ InAsSb-based superlattice (SL) long wavelength (8– $12 \mu \text{m}$) range (LWIR) cascade photodetector operating at temperatures > 190 K. The design of the detector resolves the problem of the low quantum efficiency (QE) and resistance of the traditional photovoltaic detectors optimized for high temperature (HOT) conditions. The device was deposited by molecular beam epitaxy (MBE) on GaAs substrates with type-II InAs $/$ InAsSb superlattice (T2SLs) absorbers. The constituent stages of the cascade are connected by the low resistance tunnel junctions. Detectivity ($D^{\ast }$) of the unbiased device reaches ~ $6.7\,\,\times10$ 8 cmHz $^{1/2} /\text{W}$ at 210 K, $\lambda $ = $10 \mu \text{m}$. [ABSTRACT FROM AUTHOR]

In this paper, we report on the influence of molecular beam epitaxial (MBE) growth temperature on the spectral response of the long-wavelength infrared radiation (LWIR), three-stage thermoelectrically (TE) cooled (T = 210, 230 K) InAs/InAsSb type-II superlattice (T2SL)-based detectors grown on the GaSb/GaAs buffer layers/substrates. Likewise, antimony (Sb) composition and the superlattice (SL) period could be used for spectral response selection. The presented results indicate that the growth temperature affects the 50% cut-off (λ50%cut-off) of the fabricated devices and could be used for operating wavelength tunning. Assuming constant Sb composition and T2SL period during MBE process, the growth temperature is presented to influence λ50%cut-off covering entire LWIR (e.g., temperature growth change within the range of 400–450 °C contributes to the λ50%cut-off ~ 11.6–8.3 μm estimated for operating temperature, T = 230 K). An increase in temperature growth makes a blueshift of the λ50%cut-off, and this is postulated to be a consequence of a modification of the SL interfaces. These results show an approach to the T2SL InAs/InAsSb deposition optimization by the growth temperature in terms of the spectral response, without influencing the T2SLs' structural properties (Sb composition, SL period). [ABSTRACT FROM AUTHOR]

This paper presents large area multiple photodetectors of the MOCVD grown HgCdTe heterostructures for operation at temperatures of (200-300)K in the long wavelength infrared range. Conventional long wavelength photovoltaic detectors operating at higher temperatures suffer from low dynamic resistance and multiple photodetectors idea solves this problem. Particular experimental steps are demonstrated starting from MOCVD technology, through etching, angled ion milling, angled contact metal deposition, assembly and electro-optical measurements. MOCVD technique with wide range of composition and donor/acceptor doping and without post growth annealing provides HgCdTe heterostructures for uncooled multiple detectors. CdTe buffer layer deposition allows HgCdTe heterostructure growth on GaAs substrates. Angled ion Ar+ milling optimal selection parameters is crucial for proper junction formation and conductivity type conversion. Theoretical modelling using APSYS platform supports designing of the detector’s structures. Presented technology enable to fabricate large area ($4\times 4$ mm2) multiple photodetectors with detectivity $\text{D}^\ast $ exceeding 107 cmHz $^{1/2}\text{W}^{-1}$ at $10.6~\mu \text{m}$ and room temperature operation useful for many applications. [ABSTRACT FROM AUTHOR]

This article concerns the temperature dependence of low-frequency noise measured in the temperature range of 77–300 K in InAs/InAsSb superlattice photoconductors optimized for long-wavelength infrared (LWIR) and very long-wavelength infrared (VLWIR) spectral range. The differences in the T-dependence and the magnitude of 1/f noise, observed for LWIR and VLWIR photoconductors, are connected with different scattering mechanisms. Using the Hooge empirical model of 1/f noise and modeling of the total mobility, it is suggested that either the phonon-related or the defect-related mobility fluctuations can be responsible for the measured noise depending on the mechanism which determines the total mobility. In the VLWIR photoconductors, the defect-related 1/f noise prevails, while the phonon-related component dominates in the LWIR detector. The latter is best described by the Melkonyan et al.’s mobility fluctuation model, which assumes the phonon scattering as the origin of 1/f noise. It roughly explains the T-dependence and predicts the value to within the one order of magnitude. [ABSTRACT FROM AUTHOR]

Herein, an nBn barrier mid‐wave infrared InAs/InAsSb (xSb = 0.4) type‐II superlattice (T2SL) detector operating in the thermoelectrical (TE) cooling condition is reported. AlAsSb (Sb‐composition, xSb ≥ 0.975) is shown not to introduce an additional barrier in the valence band in the analyzed temperature range (≥200 K) reached by four‐stage TE cooling in nBn barrier architectures with a T2SL InAs/InAsSb active layer. The dark current and photocurrent produced are analyzed in relation to the barrier and contact layer doping, with the Sb composition of the barrier indicating the optimal architecture. The results of the simulation are compared with the experimental results of the HgCdTe and InAsSb nBn barrier detectors. A detectivity of ≈1010 cmHz1/2 W−1 at 200 K is reported without an immersion lens (≈1011 cmHz1/2 W−1 is reported for an immersed detector). [ABSTRACT FROM AUTHOR]

We present a comparison of two interband cascade detectors optimized for long-wavelength infrared region: with equal and matched-absorbers. In matched-absorbers architecture, the first absorber determinates the thickness of the subsequent active layer, in order to meet equal quantum efficiency in all stages (QE condition). The simulations showed that quantum efficiency, for both types of architectures, decreases, while the detectivity versus number of stages increases. Detectors with equal absorbers (no QE condition) allow to build more stages in the cascade being the possible way to improve detectivity. On the other hand, structures with matched-absorbers show more flexibility in detectivity improvement by optimal selection of individual active layers. It is shown that structures assumed in this paper do not fully exploit the potential offered by the matched-absorbers approach. The optimal absorber selection allows to reach two times higher quantum efficiency. Moreover, interband cascade detectors optimized for long-wavelength were compared with intersubband quantum cascade infrared photodetectors and HgCdTe showing potential for room temperature operation. [ABSTRACT FROM AUTHOR]

This paper reports on N+- $\pi $ interface influence on the performance: dark current and response time of multilayer long-wave infrared mercury cadmium telluride (MCT - HgCdTe) N+ \pi$ P+p+n+ detector under high operating temperature conditions, T = 230$ K. A detailed analysis of the dark current and response time as a function of device architecture, i.e., N+- \pi at T = 230$ K was reduced from \approx ~62$ to 12 A/cm , while response time could be reduced to $\approx ~52$ ps for low-voltage operation, $V = 200$ mV. [ABSTRACT FROM PUBLISHER]

In this letter, we report on the InAs/InAsSb type-II superlattice (T2SL) detector operating with 50% cut-off wavelength ($\lambda _{\mathbf {c}})~\sim ~15~\mu \text{m}$ for temperatures (T) reached by three-stage thermoelectric (TE) cooling to minimize the detector’s volume to reach size, weight, and power (SWaP) conditions. The presented device reaches detectivity (D *) ~ 10 9 Jones ($\lambda _{\mathrm {c}}\sim ~15~\mu \text{m}$). These results are the first reported on single pixel T2SL InAs/InAsSb photoconductor with $\lambda _{\mathrm {c}}\sim ~15~\mu \text{m}$ where GaAs immersion lens (IL) was implemented and integrated with three-stage Peltier TE cooler. [ABSTRACT FROM AUTHOR]

InAsSb is considered as an alternative to HgCdTe ternary alloy as far as infrared (IR) detection systems are concerned. Lately, there has been an enormous progress in the development of InAsSb focal plane arrays. High-operating-temperature conditions were successfully achieved with AIII BV unipolar barrier structures including InAsSb/AlAsSb and InAs/AlAsSb material systems. The performance of medium-wavelength IR InAsSb-based nBnnn+ detectors is examined theoretically. Since there is no depletion layer in the active layer of such devices, the generation-recombination and trap-assisted tunneling mechanisms are suppressed, leading to lower dark currents in bariode detectors in comparison with standard diodes. Detailed analysis of the detector performance (such as dark current, dynamic resistance area product, and detectivity) versus bias voltage and operating temperatures are performed by pointing out optimal working conditions. The theoretical predictions of bariode parameters are compared with experimental data published in the literature. Finally, the bariode performance is compared with standard InAsSb photodiodes operated at room temperature. [ABSTRACT FROM AUTHOR]

• 3TE LWIR T2SLs InAs/InAsSb p+BnN+ detector with AlSb barrier was designed, grown and processed for CH 4 detection. • LWIR, λ ~8 µm was used for CH 4 detection as an alternative to SWIR and MWIR CH 4 lines. • Two CH 4 absorption lines at wavelengths of 7.66 µm and 7.92 µm were selected. • 33 ppb CH 4 detection limit was demonstrated in LWIR for λ ~8 µm. [Display omitted] We report on the Ga-free InAs/InAsSb type-II superlattice (T2SL) based long wavelength infrared radiation (LWIR) methane (CH 4) sensor operating at ~ 8 µm under thermoelectric (TE) cooling conditions. The presented device reaches detectivity (D *) ~ 2 × 109 Jones (~ 8 µm), current responsivity (R i) ~ 0.22 A/W, time constant (τ) ~ 14 ns. The CH 4 detection module's bandwidth (BW) was estimated at the level of 11.3 MHz. That allows to detect CH 4 at the level of ~ 33 ppb in the LWIR region. The data that support the findings of this study are available from the corresponding author upon reasonable request. [ABSTRACT FROM AUTHOR]

Mid-wave infrared technology is dominated by HgCdTe ternary alloy. As of now, InAs/GaSb type-II superlattice has shown the theoretical potential to compete with HgCdTe. Type-II superlattice InAs/GaSb technology is under development, where proper detector’s architecture must be considered as one of the most important steps in terms of performance improvement. The letter presents the performance of the type-II superlattice InAs/GaSb with bulk AlGaSb barrier, mesa type nBn detectors operated under higher operation temperature condition (>200 K) with 50% cutoff wavelength \sim 5.1~\mu \textm at 230 K. The 1.1-mm-thick GaAs substrate was converted into immersion lens to limit the influence of the defects occurring during growth on GaAs substrate and to increase detectivity, \sim 10^10 cmHz ^\mathrm 1/2 /W at 230 K, under reverse bias 200 mV and \sim 3 \times 10^9 cmHz ^\mathrm 1/2 /W at 300 K, under 400 mV. Presented results are higher than nBn architectures with the same and slightly higher cutoff wavelength grown on GaAs without immersion lens and GaSb substrates. [ABSTRACT FROM PUBLISHER]

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]

• 1/f noise from leakage current exceeds 1/f from the g–r/diffusion currents. • The leakage current from 1/f noise prevails for diffusion-limited InAsSb detectors. • Detectivity for fast/slow varying signals are determined by different currents. The 1/f noise in midwavelength InAsSb- and HgCdTe-based unipolar barrier infrared detectors, grown on GaAs substrate, are studied both experimentally and theoretically. The examination of the dark current reveals three current components: leakage, diffusion, and generation-recombination. The first dominates in the low-temperature region for all devices, while diffusion and generation-recombination components dominate in the high-temperature region. For InAsSb-based detectors with cut-off wavelength 5.6 μm at 230 K, the measured 1/f noise can be exclusively attributed to the leakage current (which has the surface origin), which means that noise coefficients (relative noise) of generation-recombination and diffusion currents are small with respect to the leakage-current induced 1/f noise. In the HgCdTe-based barrier detector with cut-off wavelength 3.6 μm at 230 K, all current components induce measurable 1/f noise, but the leakage current is effectively suppressed, consequently, 1/f noise connected with generation-recombination and diffusion currents can be isolated. For this detector, the relative 1/f noise of generation-recombination and diffusion current decrease versus temperature with an exponential manner but the relations between 1/f noise coefficients, observed for InAsSb-based devices, hold true. Then, an important conclusion is that the improvement in the above sensors detectivity, for slow varying signals, can be achieved by reducing the leakage current which can be the source of 1/f noise even at room temperature, where the total current is dominated by the diffusion component. [ABSTRACT FROM AUTHOR]

• An interband cascade long wavelength infrared detector designed for high operating temperature (≥196 K) is presented. • The "Ga-free" InAs/InAsSb superlattice with highly doped p+/n+ tunneling junctions connecting adjacent stages was used. • The 3 - stage device reached detectivity ∼3 × 107 cmHz1/2/W at 300 K and 10 % cut-off wavelength of ∼10.5 μm. • The device exhibits higher performance than multi-junction PVM HgCdTe detector optimized for 10.6 μm reaching ∼1.3 × 107 cmHz1/2/W, for 9.8 μm and 300 K. This paper presents the performance of an interband cascade long wavelength infrared detector designed for high operating temperature (≥196 K). The device was based on the "Ga-free" InAs/InAsSb superlattice with highly doped p+/n+ tunneling junctions connecting adjacent stages. The 3 - stage device reached detectivity ∼3 × 107 cm Hz1/2/W at 300 K and 10 % cut-off wavelength of ∼10.5 μm. The device exhibits higher performance than multi-junction PVM HgCdTe detector optimized for 10.6 μm reaching ∼1.3 × 107 cm Hz1/2/W, for 9.8 μm and 300 K. [ABSTRACT FROM AUTHOR]