Spontaneous and stimulated emission from CdxHg1−x Te semiconductor films

The experimental data on observation of spontaneous and stimulated emission from thin epitaxial Cd_xHg_1?x Te films optically pumped by Nd: YAG laser radiation are reported. A simple theoretical model is suggested to describe the initiation of population inversion under these conditions. The parameters realized under the experimental conditions are theoretically estimated.     

Blue-shift in photoluminescence of ion-milled HgCdTe films and relaxation of defects induced by the milling

Simultaneous measurements of electrical conductivity, the Hall coefficient, and photoluminescence (PL) spectra of ion-milled Hg_1 − xCd_xTe films (x ∼ 0.30 and 0.38) were performed during post-milling ageing of the films at 293 K. In the course of the PL study, a ‘relaxation’ of the blue-shift of the PL band of ion-milled Hg_0.70Cd_0.30Te was observed. The relaxation was caused by the decrease of the electron concentration due to gradual disintegration of defects induced by the milling. It is shown that while ion milling substantially changes the electrical properties of Hg_1 - xCd_xTe, its PL spectrum in the long-term is affected insignificantly.     

Ion-beam-induced modification of the electrical properties of vacancy-doped mercury cadmium telluride

The effect of ion-beam milling (IBM) on the electrical properties of vacancy-doped mercury cadmium telluride (MCT) p-Hg_1−x Cd _x Te (x ∼ 0.22) has been studied. The samples were prepared by thermal annealing of molecular beam epitaxy (MBE)-grown heterostructures and the films and single crystals grown by liquid-phase epitaxy (LPE). The etching of samples by IBM resulted in the formation of donor centers. In MBE-grown heterostructures (but not in LPE-grown samples), the concentration of these centers reached ∼10¹⁷ cm⁻³. It is established that the appearance of a high concentration of donor centers in the heterostructures is caused by the IBM-induced activation of neutral defects formed during epitaxial growth. The probable nature of defects is discussed.     

Infrared focal plane assemblies based on HgCdTe/Si(310) heterostructure

It is demonstrated for the first time that high-performance scanning infrared (IR) focal plane assemblies of the 288 × 4 format for long-wavelength (8–12 μm) IR spectral range can be created based on a Cd _x Hg_{1 − x} Te/Si(310) heterostructure.     

Defects in heteroepitaxial CdHgTe/Si layers and their behavior under conditions of implanted p +-n photodiode structure formation

The impurity-defect structure of heteroepitaxial Cd _x Hg_{1 ? x} Te/Si (0.35 < x < 0.39) layers grown by molecular beam epitaxy for the creation of arsenic-ion-implanted p ⁺-n junctions has been studied by the photoluminescence method. It is established that full realization of the possibilities of p ⁺-on-n photodiode structures based on the CdHgTe/Si system is hindered by uncontrolled doping of the material that leads to the formation of both shallow (impurity level energy ～10 meV) and deep (～50 meV) acceptor levels.     

CdHgTe heterostructures on large-area Si(310) substrates for infrared photodetector arrays of the short-wavelength spectral range

Heteroepitaxial structures n-Cd _x Hg_{1 ? x} Te for the near-infrared spectral range (x ≈ 0.4) are grown by molecular beam epitaxy on Si(310) substrates 72.6 and 100 mm in diameter. High composition homogeneity over the structure area is attained; the variation in x for 100-mm wafers is 0.015–0.025. During growth, the mercury-cadmium telluride (MCT) layers are doped with In with the concentration (0.5–3) × 10¹⁵ cm^?3. The magnetic-field dependences of the Hall effect are studied in the range of magnetic fields 0.05–1.0 T at liquid-nitrogen and room temperatures. The experimental values of the electron mobility at room temperature are close to the calculated ones, while at liquid-nitrogen temperature, they are lower than the calculated mobilities. The possible causes of this phenomenon such as the influence of the MCT transition layer at the interface with the CdTe buffer layer and lattice defects of MCT are discussed. The variation in the concentration and mobility of charge carriers in MCT structures after activation annealing are studied.     

Properties of MIS structures based on graded-gap HgCdTe grown by molecular beam epitaxy

The effect of near-surface graded-gap layers on the electrical characteristics of MIS structures fabricated based on heteroepitaxial Hg_{1 ? x} Cd _x Te films grown by molecular beam epitaxy with a two-layer SiO₂/Si₃N₄ insulator and anodic oxide film is studied experimentally. It is shown that a larger modulation of capacitance (depth and width of the valley) is observed compared with the structures without the graded-gap layer. The field dependences of photovoltage of MIS structures with the graded-gap layers had a classical form and were characterized by a drop only in the enrichment region. For the structures without the graded-gap layer with x = 0.22, a drop in the voltage dependence of the photocurrent is observed in the region of pronounced inversion. This drop is governed by limitation of the space charge region by processes of tunneling generation via deep levels. The properties of the HgCdTe-insulator interfaces are studied.     

Evolution of the Impurity Photoconductivity in CdHgTe Epitaxial Films with Temperature

Semiconductors - The photoconductivity spectra of epitaxial CdHgTe films are investigated by Fourier-transform spectroscopy at various temperatures. Features associated with both the interband...     

Photoelectric characteristics of diodes in prototype photosensitive pixels for a monolithic array infrared photodetector

Test photodiodes in the form of mesa structures with different areas from 30 × 30 to 100 × 100 μm in size are fabricated based on a Cd _x Hg_{1 − x} Te/Si structure at x = 0.235, grown by molecular-beam epitaxy (MBE). The current-voltage characteristics of the diodes are measured in the dark and under background light conditions. The experimental results are compared with theoretical calculations. It is found that the dependence of the photodiode photocurrent and dark current on the mesa structure size appears in the mesa size ranges from 30 × 30 to 80 × 80 μm. The dark current decreases and the photocurrent increases with decreasing mesa size. The mechanisms affecting the behavior of current-voltage characteristics are discussed.     

Determining the normal and lateral dark current components in n-p photodiodes based on p-CdxHg1 ? xTe heteroepitaxial structures with x = 0.22

The effect of an external magnetic field on the dark current of photodiodes in far-IR matrix photodetector arrays fabricated by boron ion implantation into heteroepitaxial cadmium mercury telluride (CMT) layers has been studied. A new method is proposed for separately determining the lateral and normal dark current components in CMT photodiodes of the matrix photodetectors. It is established that the dark current of these photodiodes (at 77 K) with dimensions comparable with the minority carrier diffusion length is determined primarily by the lateral component.