This article presents the InAs/GaSb type-II superlattice interband cascade photodetector low-frequency noise analysis. Presented noise measurements were conducted in temperature range 77-300 K and in frequency range 1-10 kHz. The spectral characteristics of the detector noise at various voltages are analyzed. The measured power spectral density is compared to the theoretical prediction. This comparison suggests that noise estimates based on the dark current may not always be valid and the noise source is difficult to be extract. We showed two samples, one of which was characterized by a large leakage currents contribution being directly translated into increased noise.
Type-II superlattice (T2SL) interband cascade infrared detectors (IB CIDs) proved to be a promising candidate for short response time devices operating in room and higher temperatures. The current status of the higher operating temperature (HOT) T2SLs InAs/GaSb and InAs/InAsSb IB CID is presented. We compare both materials with HgCdTe alloy, which is widely described in literature. The detectivity of midwave infrared (MWIR) T2SLs InAs/GaSb and InAs/InAsSb based IB CID has been demonstrated up to 380 K.
Type-II InAs/GaSb interband supperlattice cascade infrared detectors (IB CIDs) proved to be promising candidate for short response time devices operating in room and higher temperatures. The spectral responsivity of mid-wave (MWIR) T2SLs InAs/GaSb based IB CID has been observed even up to 380 K.
Short time constant (τs) is directly related to the unique carrier transport properties of the IB CID structures, where at 380 K ~ 4 ns τs was observed. What is more, thermal generation recombination rates of IB CIDs are orders of magnitude reduced in comparison with corresponding intersubband quantum cascade infrared detectors (IC QCID) giving flexibility in higher operating temperature (HOT) applications. The most important feature is that the multiple-stage architecture is useful for improving the sensitivity of HOT detectors, where the quantum efficiency is limited by short diffusion length. Assuming that absorption depth for IR radiation is longer than the diffusion length, only a limited portion of the photogenerated carriers contribute to the quantum efficiency. That could be circumvented by fabrication of multi-stage devices where each equal stage consist of active, relaxation and barrier layers. IB CID T2SLs InAs/GaSb detector operating at 380 K exhibits Johnson noise limited detectivity at the level of ~ 108 Jones without implementation of immersion lens.
In this paper the current status of novel HOT T2SLs InAs/GaSb IB CID is presented. Analysis of the detector’s performance versus bias voltage and operating temperatures and future trends in development of the quantum cascade detectors are shown. The paper focuses on development of IR HOT detectors and potential approaches related to materials - T2SLs InAs/GaSb where IB CIDs that eliminate the cooling requirements of IR photodetectors operating in MWIR range are presented. The prediction of near future impact of that technology on infrared detector development is also shown.
The paper presents the performance of the interband cascade type-II infrared InAs/GaSb superlattice photodetectors. Such photodetectors are made up of multiple stages, which are connected in series using an interband tunneling heterostructure. Each stage can be divided into three regions: absorber region, relaxation region and interband tunneling region. Cascade configurations allows to achieve fast response detectors. Making the assumption of bulk-like absorbers, we show how the standard semiconductor transport and recombination equations can be extended to the case of multiplestage devices. We report on the dependence of the Johnson-noise limited detectivity on the absorber thickness for a different number of stages. This allows optimization of the detector architecture, necessary to achieve high value of the detectivity. For this purpose, we make comparison of collection efficiency in single- and multiple-stage devices. The collection efficiency rapidly increases with increasing the number of stages in multiple-absorber detector, especially in situation where the absorber material’s diffusion length is less than absorption depth. We show that the optimal value of the detectivity for different number of stages does not change significantly. The potential benefits of the cascade architecture are shown to be higher in long-term detection regime.
Interband cascade type-II mid-wavelength infrared (MWIR) InAs/GaSb superlattice (T2SL) detector in room temperature (300 K) is investigated. A single stage in the cascade is a double heterostructure with the absorber sandwiched between electron and hole barriers. The absorber region is non-intentionally doped and is made of MWIR 9ML InAs/9ML GaSb T2SL. At low temperatures structure has a residual doping of p-type, but at room temperature the SL is n-type with n(300K) = 1016cm-3. In this article we calculate dark current being treated as a sum of two currents: average bulk current and average leakage current, flowing through the device. Average bulk current is theoretically calculated, while the average leakage current results from a comparison of theoretically estimated bulk current and measured one. We show that it is possible to fit theoretical model to experimental data, assuming that transport in absorber region is determined by the dynamics of the intrinsic carriers. Based on the fit we estimated carrier lifetime equal about 100 ns at temperature 300 K.
In this paper interband cascade type-II InAs/GaSb superlattice photodetector in temperature range from 225 K to 300 K
is investigated. The article concerns the theoretical simulations of the detectivity characteristics of cascade detector with
equal absorber regions in each stage. The obtained theoretical characteristics are comparable to experimentally
measured, assuming that transport in absorber is determined by dynamics of intrinsic carriers. The greatest fit is observed
for overlap values which increase with decreasing temperature form 0.175 eV for 225 K to 0.132 eV for 300 K.
In this article we present the research on optoelectronic system for stand-off detection of alcohol vapours in moving cars. The idea of using commercially available cascade lasers was presented. Special attention was paid to the optical characteristics of the car windowpanes. It was shown that using 3.45 μm and 3.59 μm wavelengths the alcohol vapours inside a car can be successfully detected even for cars with different windows
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