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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 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 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 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).

The article indicates that building an active social welfare center is a challenge in the face of the crises of the modern world. Therefore, building learners and conceptual social welfare centers is crucial for solving complex social problems of the modern world. In view of the panorama of burning crises outlined in the article, the need for subjective care for residents, especially those using the support of a social welfare center, was pointed out. It was emphasized that every citizen, regardless of their living condition, must be treated with appreciation. His participation and contribution to the reconstruction of our local and global world are important. Therefore, designing an open social welfare center that is dynamic to the challenges of the modern world requires a conceptual system defining the given architecture. It is determined by the interrelated components of organizational processes - ideological, programming, communication. Within the considered architecture, the network of relations binding the physical environment of the social welfare center is significant with human actions and experiences. This "between" as a combination of "in" and "among" expresses the spatial and temporal location of the actions taken. This perceived inter-space shapes shared experiences of caring for others. Then, within the imagination of the dialogue and the element of thinking, it is possible to design activities for the renewal of the modern world in a multidisciplinary and cross-sectoral way and to co-create optimal solutions to rebuild the life condition of people. This is reflected in tender actions embedded locally but intertwined globally. Building tender actions can be treated in the category of resistance, an active response to the life of residents in conditions of a specific order and formatted institutional practices. As a result, the recognized need to build and renew the world becomes a vitally important orientation for action. The aim of the article is a theoretical reflection on the architecture of a social welfare center in the perspective of crises of the contemporary world. [ABSTRACT FROM AUTHOR]

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]

This paper presents examples of infrared detectors with mercury cadmium telluride elaborated at the Institute of Applied Physics, Military University of Technology and VIGO Photonics S.A. Fully doped HgCdTe epilayers were grown with the metal organic chemical vapour deposition technique which provides a wide range of material composition covering the entire infrared range from 1.5 µm to 14 µm. Fundamental issues concerning the design of individual areas of the heterostructure including: the absorber, contacts, and transient layers with respect to their thickness, doping and composition were discussed. An example of determining the gain is also given pointing to the potential application of the obtained devices in avalanche photodiode detectors that can amplify weak optical signals. Selected examples of the analysis of current-voltage and spectral characteristics are shown. Multiple detectors based on a connection in series of small individual structures are also presented as a solution to overcome inherent problems of low resistance of LWIR photodiodes. The HgCdTe detectors were compared with detectors from III-V materials. The detectors based on InAs/InAsSb superlattice materials achieve very comparable parameters and, in some respects, they are even superior to those with mercury cadmium telluride. [ABSTRACT FROM AUTHOR]

A theoretical analysis of the mid-wavelength infrared range detectors based on the HgCdTe materials for high operating temperatures is presented. Numerical calculations were compared with the experimental data for HgCdTe heterostructures grown by the MOCVD on the GaAs substrates. Theoretical modelling was performed by the commercial platform SimuAPSYS (Crosslight). SimuAPSYS fully supports numerical simulations and helps understand the mechanisms occurring in the detector structures. Theoretical estimates were compared with the dark current density experimental data at the selected characteristic temperatures: 230 K and 300 K. The proper agreement between theoretical and experimental data was reached by changing Auger-1 and Auger-7 recombination rates and Shockley- Read-Hall carrier lifetime. The level of the match was confirmed by a theoretical evaluation of the current responsivity and zero-bias dynamic resistance area product (R0A) of the tested detectors. [ABSTRACT FROM AUTHOR]

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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]