Stanislav M. Dzyadukh

This work presents the initial realization of a photosensitive mid-wave infrared (MWIR) nBn structure utilizing n-type HgCdTe with a superlattice barrier, achieving dark current levels comparable to the highest-performing HgCdTe-based photodiodes globally. The MWIR n-HgCdTe nB(SL)n heterostructure was designed and fabricated via molecular-beam epitaxy (MBE). Experimental investigations of its electrophysical and photoelectric properties were conducted to assess its performance metrics. The structure exhibited exceptionally low dark current values, on the order of picoamperes, at an operating temperature of 160 K. The dark current in the studied structure is compared with similar values presented by other authors, as well as with the benchmark Rule07 and Law19. A comparative analysis reveals that the fabricated photosensitive nBn MWIR structure, based on MBE-grown HgCdTe with a superlattice barrier layer, exhibits dark current density values comparable to the highest-performing global counterparts in the MWIR range. In the temperature range of 200–230 K it is possible to realize the values of dark current density close to the limit of background radiation noise.

Subject of study. The feasibility of applying superlattices as barrier layers in unipolar barrier nBn structures based on n-type HgCdTe [grown by molecular beam epitaxy (MBE)] for photodetection is investigated. Aim of study. This study aims to determine the influence of infrared optical radiation on the electrophysical characteristics of nBn structures based on HgCdTe (grown by MBE) with a superlattice in the barrier region. Method. Epitaxial Hg_1−xCd _x Te films, constituting nBn structures with a superlattice composed of 18 periods of Hg_0.2Cd_0.8Te (9 nm) and HgTe (2 nm), were grown by MBE. These films were then used to fabricate metal–insulator–semiconductor (MIS) structures. The photoelectric properties were investigated using admittance spectroscopy, both with and without 940-nm infrared light-emitting diode (LED) irradiation. Main results. Infrared optical radiation evidently affects the electrophysical characteristics of nBn structures based on HgCdTe (grown by MBE) with a superlattice in the barrier region. However, this influence does not mirror the behavior of classical MIS structures exposed to optical radiation, indicating that the superlattice contributes to the photoelectric properties of the studied structures. The observed effects are likely related to the recharging of energy levels (minibands) in the superlattice within the barrier region of the nBn structure. Practical significance. Since the application of superlattices in barrier nBn structures based on n-type HgCdTe is considered the most promising approach to eliminating the potential barrier for minority charge carriers, the results of this study may provide a foundation for developing photosensitive structure designs for the mid- and long-wave infrared ranges and for the subsequent creation of photodetector elements.

Subject of study. The application of superlattices as barrier layers in unipolar barrier nBn structures based onn-HgCdTe grown by molecular beam epitaxy is studied. Aim of study. The aim is the analysis of the current state of theoretical and experimental research on the creation of unipolar photosensitive barrier nBn structures based on Hg_1−x Cd_xTe grown by molecular beam epitaxy with superlattices as the barrier layer. Method. To achieve the aim, the results of theoretical and experimental studies of the use of superlattices as barrier layers in unipolar barrier nBn structures based on n-HgCdTe grown by molecular beam epitaxy were analyzed. Ab initio modeling of the energy diagram of superlattices in general and superlattices based on HgCdTe in particular is an extremely labor-intensive task. Therefore, the results of similar calculations performed by other authors, as well as the results of experimental studies that verify these calculations, were analyzed for the purpose of assessing the applicability of superlattices as the barrier in HgCdTe nBn structures. The goal was to determine the optimal values of the superlattice parameters based on this analysis. Main results. Based on the analysis of the results of currently known theoretical and experimental works that use superlattices as barriers in nBn structures based on n-HgCdTe, the ranges of optimal values of superlattice parameters (compositions and thicknesses of superlattice barrier layers and quantum wells) were determined. The need for additional research on the protection (passivation) of the side faces during the manufacture of experimental samples in the configuration of mesa structures to minimize the contribution of surface leakage currents to the dark current of the photosensitive structure was also noted. Practical significance. This work was aimed at analyzing the current state of the research in the area under consideration and determining which configurations of superlattice barriers seem to be optimal. As the use of superlattices in barrier nBn structures based on n-HgCdTe is considered to be the most promising way to eliminate the potential barrier for minority charge carriers, the results of this work can form the basis for developing the design of photosensitive structures in the MWIR and LWIR ranges and the subsequent creation of photodetector elements.