A. V. Voitsekhovskii

Influence of composition of the near-surface graded-gap layer on the admittance of metal-insulator-semiconductor structures based on graded-gap MBE n-Hg1−xCdxTe in wide temperature range

Influence of the CdTe content in a near-surface graded-gap layer on the admittance of MIS-structures fabricated on the basis of heteroepitaxial Hg1−xCdxTe (x = 0.22–0.23 and 0.31–0.32) films grown by molecular beam epitaxy was investigated in a wide temperature range. It is shown that a temperature drop from 77 K to 8 K results in a decrease of hysteresis of the capacitance-voltage (C-V) characteristics and a decrease of frequencies which corresponds to a high-frequency behaviour of C-V characteristics of MIS-structures based on n-HgCdTe (x = 0.22–0.23) with and without graded-gap layersand also for MIS-structures based on n-HgCdTe (x = 0.31–0.32). Temperature dependences of the resistance of the epitaxial film bulk and differential resistance of the space-charge region (SCR) in strong inversion mode were studied. The experimental results can be explained by the fact that for MIS-structures based on n-HgCdTe (x = 0.22–0.23) with the graded-gap layers and for MIS-structures based on n-HgCdTe (x = 0.31–0.32), the differential resistance of SCR is limited by Shockley-Read generation at 25–77 K. Differential resistance of SCR for MIS-structures based on n-HgCdTe (x = 0.22–0.23) without the graded-gap layers is limited by tunnelling through deep levels at 8–77 K.

Defect study in molecular beam epitaxy-grown HgCdTe films with activated and unactivated arsenic

A defect study was performed on molecular beam epitaxy-grown HgCdTe films in situ doped with arsenic. Doping was performed from either effusion cell or cracker cell, and studied were both as-grown samples and samples subjected to arsenic activation annealing. Electrical properties of the films were investigated with the use of ion milling as a means of “stirring” defects in the material. As a result of the study, it was confirmed that the most efficient incorporation of electrically active arsenic occurs at the cracking zone temperature of 700 °C. Interaction between arsenic and tellurium during the growth was observed and is discussed in the paper.

Influence of near-surface graded-gap layers on electrical characteristics of MIS-structures based on MBE grown HgCdTe

The paper examines influence of near-surface graded-gap layers on electrical characteristics of MIS-structures fabricated on heteroepitaxial Hg1−xCdxTe films grown by molecular beam epitaxy (MBE). Two types of insulators, i.e., two-layer SiO2/Si3N4 and anodic oxide films were used. As it is seen from the depth and width of the valley on the C-V characteristics, the capacitance is found to vary in a wide range, in contrast to the structures without graded-gap layers. It is shown that the graded-gap layer under MIS-structures with x = 0.22 effectively reduces the tunnelling generation via deep levels and increases a lifetime of minority carriers in the space charge region and its differential resistance. The properties of the HgCdTe-insulator interfaces 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 Hg1 − x CdxTe 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.

Critical thickness of 2D to 3D transition in GexSi1−x/Si(001) system

In this paper, Stranski–Krastanov growth of GexSi1−x epitaxial layers on the Si(001) surface is considered. Experimental investigations show that the moment of transition from 2D to 3D growth and the critical thickness of 2D layer at which this transition occurs play a key role during the synthesis of such materials. Among the most important parameters determining the peculiarities of the growth process and characteristics of emerging island ensembles are growth temperature and surface conditions (for example, the presence of surfactants). But existing theoretical models are not able to predict the values of the critical thickness in the whole range of growth temperatures and compositions x of solution for these systems. For the calculations of the critical thickness of transition from 2D to 3D growth, in this paper, a theoretical model based on general nucleation theory is proposed. This model is specified by taking into account dependencies of elastic modulus, lattices mismatch, and surface energy of th...

Capacitance-voltage characteristics of MIS-structures on the basis of graded-band MBE Hg1−xCdxTe at passivation by epitaxially grown in situ CdTe

The electrical properties of the interface between Hg1−xCdxTe (x = 0.22 and x = 0.32–0.36) and CdTe prepared in situ molecular beam epitaxy were estimated at 77 K. The methods of determination of main parameters of interface semiconductor/insulator and insulator from capacitance-voltage characteristics of MIS-structures based on graded-band Hg1−xCdxTe have been developed. The fixed charge states density, fast surface states density, and density of mobile charge are obtained from capacitance-voltage measurements. For improvement in stable and electrical strength of insulator coating for several samples over CdTe additional protective layers SiO2-Si3N4 are formed for x = 0.22 and ZnTe for x = 0.32–0.36.

High temperature electron irradiation and isochronal annealing of p-Hg1−x Cd x Te crystals

Abstract The peculiarities of defect formation in p-Hgi-x Cd x Te crystals (x=0.195−0.205) at electron irradiation (2.3 MeV, 300 K) up to 1 × 1018 cm−2 were investigated. It was shown that the charge carrier lifetime changed with the irradiation due to variation of the free charge carrier density and the recombination-type centre concentration. A distance of recombination centres from the valence band of 35–55 meV for the electron irradiated crystals is determined. The isochronal annealing temperature ranges for the recombination-type radiation defects and electrically active defects, induced by the irradiation, are found.

Ion milling-induced conductivity-type conversion in p-type HgCdTe MBE-grown films with graded-gap surface layers

In this paper, ion milling-induced conductivity-type conversion in p-type HgCdTe molecular beam epitaxy-grown films with graded-gap surface layers is studied. As expected, the chemical composition of the graded-gap layer strongly affects the conversion depth. At the composition of the layer on the surface, xv > 0.5, ion fluences typically used for fabricating p?n junctions in HgCdTe create only a damaged surface n+-layer with no deep conversion. With lower xv, conversion with controllable depth due to diffusion of interstitial mercury atoms HgI can be achieved. Defect reactions in the graded-gap surface layers under the milling and post-milling ageing, which are caused by interaction of HgI with dislocations, differ from those in the deep converted layers, where HgI reacts with point defects. It is shown that when assessing the depth of a p?n junction fabricated with ion milling in HgCdTe with a graded-gap surface layer, it is necessary to consider the effect of the material removal from the surface.

Energy-band diagrams and capacity-voltage characteristics of CdxHg1−xTe-based variband structures calculated with taking into account dependence of electron affinity on a composition

The purpose of this scientific work is the research of energy-band diagrams and capacity-voltage characteristics of CdxHg1−xTe-based variband heteroepitaxial structures with taking into account the dependence of electron affinity on the composition.Numerical simulations of energy-band diagrams and capacity-voltage characteristics for metal-insulator-semiconductor structures based on CdxHg1−xTe-variable composition layers are carried out in this work. Energy diagrams are calculated with taking into account the dependence of electron affinity on the composition x of CdxHg1−xTe. This dependence was obtained in terms of dependence of the local electroneutrality level on the composition for CdxHg1−xTe.

Photoelectric Properties of Photodetectors Based on Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

We have calculated the spectral, threshold, and noise characteristics of p-Si–PtSi photodetectors with highly-doped surface layers produced by molecular-beam epitaxy and short-pulse ion implantation by a recoil method.