G. Yu. Sidorov

Dependence of the electrical parameters of MBE-grown CdxHg1 − xTe films on the level of doping with indium

Dependences of the minority-carrier lifetime and electron mobility in CdxHg1 − xTe films on their indium-doping level are studied. Films with x ≈ 0.22 grown by molecular-beam epitaxy on GaAs substrates were in situ doped with indium across their entire thickness. The temperature dependences of the lifetime were studied in the temperature range 77–300 K. The decrease in the lifetime, observed as the doping level increases, is governed by the mechanism of Auger recombination. As the doping level becomes higher, the mobility decreases in qualitative agreement with theoretical calculations.

High-performance 320 × 256 long-wavelength infrared photodetector arrays based on CdHgTe layers grown by molecular beam epitaxy

This paper gives the parameters of 320 × 256 element long-wavelength infrared photodetectors fabricated by a new improved technology based on heteroepitaxial mercury-cadmium-tellur structures. In these photodetectors, the variation of the photodiode bias voltage over the area of the array is minimized; inefficient photodiode regions related to both hybridization and spike-shaped growth defects of epitaxial films are eliminated; the current-voltage characteristics of the diodes in the resulting photodetectors are homogeneous and are limited by the diffusion current component up to −400 mV. The dark current is 0.25–0.45 nA, and R0A = (0.6–3) · 102 Ω · cm2. The voltage sensitivity, the threshold irradiance, and the average NETD at the maximum sensitivity are 11.8 · 108 V/W, 3.7 · 10−8 W/cm2, and 26.8 mK, respectively. The percentage of defective elements is 1.5%.

Effect of annealing on the optical and photoelectrical properties of CdxHg1 − xTe heteroepitaxial structures for the middle infrared range

We have studied the influence of various postgrowth treatments (annealing in helium atmosphere or mercury vapor, low-energy ion etching) on the optical and photoelectrical properties of mercury cadmium telluride (CdxHg1 − xTe) heteroepitaxial structures for the photo- and optoelectronic devices operating in the middle infrared range (3–5 μm). It is established that the annealing in mercury vapor is optimum for improving the photoluminescence characteristics in this range.

Photoluminescence of CdHgTe epilayers grown on silicon substrates

We have studied the photoluminescence (PL) spectra of thin layers of mercury cadmium telluride (CdHgTe) solid solutions grown by molecular beam epitaxy on silicon substrates. It is established that a disorder in the solid solution structure in these layers does not exceed that in the layers grown by the same method on GaAs substrates. The PL spectra of CdHgTe/Si samples exhibit emission lines characteristic of the structurally perfect material, in particular, the lines due to donor-acceptor recombination and the recombination of excitons bound to impurities.

Effect of post-implantation annealing on the current-voltage characteristics of IR photodiodes based on p-HgCdTe

Current-voltage characteristics of IR photodiodes and distributions of charge carriers in n+-n−-p-structures based on vacancy p-doped Hg1 − xCdxTe films with x = 0.22 are examined. Three-dimensional numerical modeling of the distribution of charge carriers and current-voltage characteristics during photodiode annealing is performed. The calculations predict that large tunnel currents in diodes after implantation can result from an elevated (more than 1015 cm−3) concentration of donors in the n−-layer, which enhances tunneling by decreasing the thickness of the space charged region of the n-p-junction, and also from a small (less than 3 µm) depth of the p-n-junction.

1.5–1.8 μm photoluminescence of MBE-grown HgCdTe films

The photoluminescence (PL) of HgCdTe films grown by molecular beam epitaxy (MBE) has been studied in the 1.5–1.8 μm wavelength range. The post-growth annealing of samples for 20 h at 270°C in an inert atmosphere leads to changes in the spectrum and intensity of luminescence. The spectral changes are related to an increasing homogeneity of the film composition in depth as a result of the mutual diffusion of alloy components. An increase in the room-temperature PL intensity is due to the improved structure of annealed films.

The influence of hydrogenation on the electrical properties of the CdxHg1 − xTe epitaxial structures

The phenomenon of hydrogenation of the CdxHg1 − xTe films is studied. Hydrogenation was performed via either boiling the CdxHg1 − xTe films in deionized water or using the electrochemical treatment. It is established that, during contacts with aqueous media, the acceptor centers are introduced into the films; their concentration can exceed 1017 cm−3. It is shown that two types of hydrogen-based acceptors are introduced, namely, fast and slow acceptors, and their diffusivities are evaluated. It is found that hydrogen partially exists after treatment in an electrically inactive form and can be activated with further storage or during heating. After activation, the hole concentration can become as high as 1018 cm−3. The influence of pH of the medium on the rate of introduction of hydrogen into the material is discussed.

Effect of the arsenic cracking zone temperature on the efficiency of arsenic incorporation in CdHgTe films in molecular-beam epitaxy

CdxHg1 − xTe films with x ≈ 0.22 and thickness of ∼10 µm have been grown by molecular-beam epitaxy on gallium arsenide substrates and doped in situ with arsenic. Activation annealing of doped films provided p-type conduction with a hole density of up to 1017 cm−3. The influence exerted by the arsenic cracking zone temperature on the efficiency of arsenic incorporation into the CdHgTe film was studied. A model describing the dependence of the arsenic concentration in the films on the arsenic cracking zone temperature was suggested. A comparison of the model and the experimental data demonstrated that the incorporation efficiency of diatomic arsenic is approximately two orders of magnitude higher than that of tetratomic arsenic.

The electrical properties of HgCdTe layers grown by MBE on Si and P + / n junction formed on its basis

We studied the electrical properties of undoped and indium-doped and arsenic-doped CdXHg1-XTe layers with x ≈ 0.3 - 0.4 grown by molecular beam epitaxy on Si (310) substrates. After the growth HgCdTe layers were annealed at mercury atmosphere. The lifetime at room temperature in the As-doped layers, do not depend on its carrier concentration. The lifetime in indium-doped layers increased after annealing at saturated mercury vapor pressure. It is explained by suppression of recombination centers density. Temperature dependence of the reverse currents of p+-n junctions fabricated in Cd0.3Hg0.7Te heterostuctures grown by MBE on Si substrates has been studied.

Concentration of Vacancies in the Metal Sublattice of Cadmium and Mercury Tellurides Solid Solutions Depending on Composition

Calculations for the concentration of vacancies in the metal sublattice of CdxHg1 − xTe ternary compound in dependence on temperature and composition in the range x = 0.2–1.0 are presented. In our calculations, the vacancy concentration was determined according to the reaction of the joining of the crystal lattices of two sites, one of which was occupied by an atom of tellurium while the site in the metal sublattice remained vacant. Using this approach, the concentration of vacancies in the metal sublattice was described via the activity of tellurium, allowing us to use it for solid solutions and a number of cases in which it is difficult to describe the pressure of the metal correctly. The enthalpy of formation was determined for vacancies in HgTe using the experimental data on the concentration of vacancies in CdxHg1 − xTe samples. It was shown that the natural oxide occurring on the surface of the investigated films in air can lead to changes in their electrophysical parameters during heat treatment.