E. F. Venger

Far infrared stimulated and spontaneous radiation in uniaxially deformed zero-gap Hg1−xCdxTe

Stimulated radiation in the range of 80–100 µm was observed in uniaxially stressed zero-gap Hg1−xCdxTe (x=0.10–0.14) under conditions of impact ionization by an electric field. The abrupt increase in emission occurs under the threshold values of elastic strain and electric-field strength and is followed by an abrupt increase in the current in the sample. The field and deformation dependences of spontaneous radiation are also determined. The mechanism of the effect observed is suggested taking into account the transformation of energy bands and impurity acceptor levels by the uniaxial elastic stress.

Strain‐Induced MI Transition in n‐Si and n‐Ge: Physical Mechanisms and Transport Phenomena

The analysis of experimental data on the pressure and temperature dependences of conductivity, the current-voltage characteristics (IVC), and the pressure dependence of the activation energy in n-Si and n-Ge crystals in the region of strain-induced metal-insulator transition (MIT) is presented. A remarkable change of the effective mass of carriers in semiconductors caused by strain-induced transformation of the energy band structure is the main necessary condition for realization of this kind of metal-nonmetal transition.

Electronic properties of a GaAs surface treated with hydrochloric acid

Processing in HCl is found to stabilize the system of surface electronic states of the (100) surface of n-GaAs in the temperature range 100–300 K. Distributions for the effective density of surface electronic states in the band gap of GaAs, which are obtained from the electric-field dependence of the surface photovoltage, depend on the measurement temperature. This is because the electronic states that affect the electric-field measurements are located both at the boundary between GaAs and the surface film and in the films themselves. Processing in HCl decreases the density of electronic states of both types, and also decreases the concentration of deep and shallow traps for nonequilibrium holes. These effects are even more pronounced when the processing in HCl is followed by washing in water.

Modification of the electrical and photoelectric properties of Mg0.15Cd0.85Te solid solutions as a result of pulsed laser irradiation within the transparency range

Changes in the equilibrium conductivity and photoconductivity of Mg0.15Cd0.85Te solid solutions exposed to pulsed laser radiation at a frequency from the transparency range of the crystal are studied as a function of the laser fluence. An increase in the photoconductivity and a shift of the photoconductivity long-wavelength limit to higher energies are found. A change in the electrical properties of the crystals is attributed to an increase in the concentration of donors with ionization energies E1=0.015 eV and E2=0.035 eV in the surface region. Possible causes and mechanisms of the changes in the photoelectric properties of the II-VI crystals exposed to laser radiation are analyzed.

The transition layer in TiB2-GaAs and Au-TiB2-GaAs Schottky contacts

Spectral characteristics of the transverse bulk photovoltage in the TiB2-GaAs and Au-TiB2-GaAs Schottky contacts for starting samples (unannealed) and samples annealed at 400, 600, and 800°C were measured. The concentration of the dopant for the n-GaAs substrate was 1016 cm−3. It was found that the transition layer is formed in the TiB2-GaAs structures owing to the diffusion of boron atoms into the GaAs substrate. Thermal annealing leads to an increase in the doping level of the layer. For the Au-TiB2-GaAs structure, the transition layer is formed, with the doping level of this layer being weakly affected by thermal annealing. The spectral position of the bulk-photovoltage peaks indicates that the tails of the density of states are formed in the band gap of the semiconductor transition layer owing to an increase in the dopant concentration to 1017–1018 cm−3.

Thermal donors and radiation-induced defect states in transmutation doped gamma-irradiated silicon

Transport phenomena are studied in uniaxially strained transmutation doped γ-irradiated n-Si(P) crystals. It is shown that thermal annealing of the transmutation doped Si results in the generation of different types of thermodonors. Tensoresistivity mechanisms in highly strained transmutation doped silicon are identified as well.

Defect states in transmutation-doped γ-irradiated Cz-Si crystals under high uniaxial pressure

In order to identify tensoeffect mechanisms in neutron transmutation doped (NTD) n-Si(P), the tensoresistive and tenso-Hall effects were investigated in highly strained crystals with phosphorous concentration 3 × 10 13 -7.2 × 10 14 cm -3 and under different doses of γ-radiation (up to 8 x 10 17 quanta/cm 2 ). It was determined that according to the defect structure and its corresponding energy level within the band gap, an appreciable decrease of the activation energy of different types of radiation-induced defects and accompanied increase of the concenration of free electrons occur in different range of uniaxial pressure. The mechanism indicated above together with the intervalley redistribution of electrons (Smith-Herring mechanism) and pressure dependence of the f-scattering probability determine tensoeffect peculiarities which were investigated in highly strained NTD and γ-irradiated Si(P).

The effect of composition on the properties and defect structure of the CdS-Ga2S3 solid solution

The effect of excess CdS in gallium thiogallate (CdGa2S4) on the spectrum of defect states in its band gap is investigated. Comparative investigations of Raman, photoluminescence, and cathodoluminescence spectra, as well as of the kinetics of photoconductivity in starting crystals (type A) and crystals obtained in conditions with excess CdS (type B), were carried out. It was found that the main types of defects in type A crystals are Cd and S vacancies, antisite GaCd donor defects, as well as IS defects, which are caused by the incorporation of carrier gas. In type B crystals, along with IS, the main defects are antisite acceptor defects CdGa as well as interstitial atoms Cdi and Si. It is demonstrated that the emission characteristics of the crystals investigated are determined by associations of the above defects. A luminescence band peaked at hνm=0.971 eV was observed for the first time. This band is related to intracenter transitions in the d shell of Cd of the CdGa defect, which is split due to the effects of the crystalline field and spin-orbit interaction, in the presence of Si.

Emission Associated with Extended Defects in Epitaxial ZnTe/GaAs Layers and Multilayer Structures

It was shown by the methods of X-ray diffraction and photoluminescence that the use of a thin intermediate recrystallized ZnTe layer between the ZnTe buffer layer obtained by molecular-beam epitaxy and GaAs substrate, as well as an increase in the thickness of the epilayer result in the improvement of the structure (enhancement of the mosaic size) and an increase in the intensity of exitonic bands. It is established that a number of characteristics of the I1C bands with hν≈2.361 eV, which are observed in the samples with quantum wells and superlattices, differ from the corresponding features of the emission lines of free and bound excitons and those lines typical of dislocation-related radiation in II-VI single crystals. It is assumed that the I1C band is associated with the subblocks boundaries, which comprise the mosaic structure of epitaxial layers.

Breakdown of shallow-level donors in Si and Ge on the insulating side of a strain-induced metal-insulator transition

Impact ionization of electron localized states on the insulating side of a strain-induced metal-insulator transition in Si:P and Ge:Sb crystals was investigated for donor concentrations appreciably exceeding the critical concentration for a transition caused by variations in the impurity concentration. Dependences of the activation energy and impact-ionization field on uniaxial stress were derived. Transitions from metallic-type conductivity to ɛ2-conductivity in the region of high uniaxial pressures are analyzed on the basis of the transformation of the conduction band energy spectrum along a certain direction of the deformation axis in silicon and germanium crystals.