Analysis of operation of a photoresistor based on CdxHg1−xTe at high bias currents

The photoresponse signal and the spectral density of the charge carrier fluctuations are calculated as functions of the frequency for a photoresistor based on n-type Cd_xHg_1–xTe at various bias currents. It is shown that when the photocarrier time of flight is shorter than their lifetime the threshold power of the photoresistor is observed to rise owing to the effect of minority carriers being extracted from the photoresistor bulk. The threshold sensitivity of the photoresistor was analyzed over a wide range of frequencies with allowance for the thermal noise at various values of the parameters of the semiconducting material of the sensitive element and recording circuits. It was found that the limitations of photoresistor circuits with a constant bias can be overcome by employing contactless switching of a cadmium mercury telluride semiconductor specimen in a microwave resonator.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 125–130, June, 1978.     

Lifetime in compensated p-cdxHg1−xTe (x ≃0.3) crystals with deep acceptors

A complex study is made on the recombination process in p-type Cd_xHg_1–xTe (x 0.3) crystals with equilibrium carrier concentrations at 77 K that are close to intrinsic. It is established that the lifetime is substantially limited by recombination through deep acceptor levels situated at 70 MeV above the v-band. An analysis is made on the statistics of Shockley-Read recombination allowing for an arbitrary level of acceptor compensation. Methods are proposed and acceptor parameters are determined: alloying depths, concentrations, and nonequilibrium charge carrier capture cross-sections.Translated from Izvestiya Vysshikh Uchbnykh Zavedenii, Fizika, No. 2, pp. 42–46, February, 1988.The authors are grateful to L. F. Linnik for his help in the laser measurements and for valuable discussions.     

Lifetime of charge carriers in Hg1-xCdxTe (x=0.20) crystals

We examine the mechanisms for Auger recombination in narrow-gap semiconductors of the Hg_1-xCd_xTe type, connected with collision between two electrons in the E_c band followed by transition of one of them to the E_v1 band and collision between two holes in the E_v1 band followed by transition of one of them to the E_v2 band. In analyzing the contributions from different recombination mechanisms over broad concentration and temperature range, we used the models of P. E. Petersen and B. L. Gel'mont, taking into account the specific characteristics of the band structure of Hg_1-xCd_xTe crystals. We determined the temperature and concentration ranges for n- and p-type semiconductors in which different recombination mechanisms are realized, including a radiative mechanism. We compare the experimental data on charge carrier lifetime with the calculation results using different recombination models in the crystals under study.V. D. Kuznetsov Siberian Physicotechnical Institute at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 99–104, February, 1994.     

Detection of terahertz and sub-terahertz wave radiation based on hot-carrier effect in narrow-gap Hg<Subscript>1−x</Subscript>Cd<Subscript>x</Subscript>Te

We have proposed and developed terahertz and subterahertz wave detector using hot-carrier effect in narrow-gap Hg_1−xCd_xTe. Epitaxial Hg_1−xCd_xTe-layers were integrated into dipole antennas. The response of Hg_1−xCd_xTe hot-electron bolometer was measured in the range of frequencies 0.037–1.58 THz, in the temperature region T = 68–300 K at various bias currents. A bolometer theoretical model was developed and the experimental results confirm the model main conclusions.     

Stress relaxation in CdHgTe/CdTe heterostructures

Based on our analysis of the results of measurements of elastic deformation in Cd_xHg_1–xTe/CdTe heterostructures it is shown that the degree of relaxation of the crystal lattice for Cd_0.2Hg_0.8Te films 1 µm thick with a working temperature of 273 K is 0.8766, which supports the idea of almost full relaxation of the mismatch stress for such thicknesses of A₂B₆ films.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 112–114, August, 1995.     

Effect of temperature on the band structure of MnxHg1−xSe

The band structure of the solid solutions Mn_xHg_1–xSe is constructed on the basis of the band parameters obtained from the electrophysical and optical investigations of these solid solutions. It is shown that the band structure of Mn_xHg_1–xSe and the dynamics of the bands as a function of the composition and temperature are analogous to those for Cd_xHg_1–xTe. It is shown that the variation of the nonparabolicity of the band spectrum of Mn_xHg_1–xSe as a function of the temperature greatly affects the temperature coefficient of the change of the width of the optical forbidden band (d_gop/dT).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 40–44, April, 1991.     

Recombination of nonequilibrium charge carriers in epitaxial Hg1−x Cdx Te MBE films

We present the results of charge-carrier lifetime measurements in narrow-band Hg_1−xCd_xTe epitaxial structures (x=0.210–0.225) grown by molecular-beam epitaxy (MBE) using pulsed excitation by radiation at various wavelengths. In p-type epitaxial films the carrier lifetime is governed by Shockley-Read recombination at impurity-conduction temperatures. The governing factor for n-type epitaxial films is Auger recombination, with some contribution from other recombination mechanisms (surface and macrodefects). V. D. Kuznetskov Siberian Physicochenical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 96–101, September, 1997.     

Modeling of the Interaction of High-Power Pulsed Ion Beams with Cadmium-Mercury-Tellurium Semiconductor Targets

A mathematical model for describing the interaction between high-power pulsed ion beams and semiconductor Cd_xHg_1–x Te (cadmium–mercury–tellurium or CMT) targets is developed, the results of numerical simulation are reported, and the comparison with experiment is performed.     

Influence of alloy composition on the diffusivity-mobility ratio in n-channel inversion layers on ternary semiconductors

An expression is derived for the diffusivity-mobility ratio of the carriers in n-channel inversion layers on semiconductors like the ternary compounds which have strongly non-parabolic energy bands. The dependence of the ratio on alloy composition is also studied under the weak-field limit taking n-channel Hg_1–xCd_x.Te as an example.On leave of absence fromthe Department of Physics, Patna University, Patna, India.     

Theoretical analysis of the gate capacitance inn-channel inversion layers on ternary chalcopyrite semiconductors in the presence of a quantizing magnetic field

An attempt is made to study theoretically, the dependence of the gate capacitance inn-channel inversion larges on ternary chalcopyrite semiconductors on a quantizing magnetic field, takingn-channel inversion layers on CdGeAs₂ as an example. It is found, on the basis of a newly derived electron energy spectrum of the above class of semiconductors, that the gate capacitance exhibits spiky oscillations with changing magnetic field and the oscillatory behaviour is in qualitative agreement with the experimental observation reported in the literature for the MOS structure of Hg_1–x Cd _x Te.     

On the gate capacitance of MOS structures of kane-type semiconductors under magnetic quantization

An attempt is made to formulate the gate capacitance of MOS structures of Kane-type semiconductors under magnetic quantization, without any approximations of weak or strong electric field limits, on the basis of the fourth-order effective mass theory and taking into account the interactions of the conduction, light-hole, heavy-hole, and split-off bands. It is found, taking n-channel Hg_1–x Cd _x Te as an example, that the gate capacitance exhibits spiky oscillations with changing magnetic field, which is in qualitative agreement with experimental observations, reported elsewhere, in MOS structures of the same semiconductor. The corresponding results for n-channel inversion layers on parabolic semiconductors are also obtained from the expressions derived.     

Effects of in situ thermal annealing on the structural, optical, and electrical properties in Hg0.7Cd0.3Te epilayers grown on CdTe buffer layers

Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) transmission, and Hall effect measurements were performed to investigate the structural, optical, and electrical properties of as-grown and in situ-annealed Hg_0.7Cd_0.3Te epilayers grown on CdTe buffer layers by using molecular beam epitaxy. After the Hg_0.7Cd_0.3Te epilayers had been annealed in a Hg-cell flux atmosphere, the SEM images showed that the surface morphologies of the Hg_0.7Cd_0.3Te thin films were mirror-like with no indication of pinholes or defects, and the FTIR spectra showed that the transmission intensities had increased in comparison to that of the as-grown Hg_0.7Cd_0.3Te epilayer. Hall-effect measurements showed that n-Hg_0.7Cd_0.3Te epilayers were converted to p-Hg_0.7Cd_0.3Te epilayers. These results indicate that the surface, optical, and electrical properties of the Hg_1 − xCd_xTe epilayers are improved by annealing and that as-grown n-Hg_1 − xCd_xTe epilayers can be converted to p-Hg_1 − xCd_xTe epilayers by in situ annealing.     

Diluted magnetic semiconductor superlattices and heterostructures

Diluted magnetic semiconductors (DMS) are mixed semiconducting crystals whose lattice is made up in part of substitutional magnetic ions. Cd_1−xMn_xTe and Hg_1−xMn_xTe are examples of such materials. Their structural and band parameters can be “tuned” by composition over a wide range. They can thus be exploited in situations completely similar to those involving Ga_1−xAl_xAs. Using molecular beam epitaxy, we have grown Cd_1−xMn_xTe superlattices with alternating Mn content, having up to 150 layers, with layer thickness ranging from 50 to 100 Å. The superlattice structure is clearly revealed by transmission electron microscopy and by zone-folding of the phonon spectrum observed in Raman scattering. Photoluminescence observed on Cd_1−xMn_xTe superlattices is several orders of magnitude greater than that from a Cd_1−xMn_xTe film with uniform Mn content, or from bulk Cd_1−xMn_xTe specimens. The presence of localized magnetic moments in DMS results in a strong exchange interaction between these moments and band electrons. This in turn leads to gigantic Zeeman splittings of impurity states, exciton levels, Landau levels, and the bands themselves. Zeeman splittings as large as 20 meV (which in non-magnetic semiconductors would require unrealistic megagauss fields) are easily achieved in DMS in fields of several kilogauss. Since the magnitude of this exchange-induced splitting in DMS can be comparable to the binding energies and to the minigaps encountered in multiple quantum wells, DMS superlattices hold promise of a host of novel effects of both fundamental and applied interest.     

Hg1-xCdxTe禁带以上的本征光吸收

讨论了HgCdTe三元半导体在能量大于禁带宽度范围内的本征吸收光谱。经过分析比较实验数据,Kane理论结果以及几种经验公式,指出Anderson从Kane模型获得的理论公式及褚君浩等从实验结果得出的经验公式,最符合HgCdTe禁带以上本征光吸收行为。文中还就外延薄膜样品的本征吸收进行了讨论。 关键词：     

Quantum efficiency of photoconductive detectors—influence of reflection and surface recombination velocity

In this work, analytical expressions determining the quantum efficiency at low electric fields, taking into account reflections at front and back detector surfaces and corresponding surface recombination velocities, are obtained.Using these expressions, the dependence of the quantum efficiency of Hg_1−xCd_xTe photoconductive detectors on the wavelength of the incident radiation for x = 0.215, at liquid nitrogen temperature, is calculated.     

Theoretical analysis of the oscillatory gate capacitance inn-channel inversion layers on ternary chalcopyrite semiconductors under magnetic quantization

An attempt is made to investigate theoretically the gate capacitance inn-channel inversion layers on ternary chalcopyrite semiconductors under both weak and strong electric field limits in the presence of a quantizing magnetic field, takingn-channel inversion layers on p-type Cd GaAs₂ as examples. It is found, on the basis of the newly derived 2D electron spectra in inversion layers on the above class of semiconductors, for both weak and strong electric field limits, that the gate capacitances oscillate with the quantizing magnetic field and the crystal field splitting parameter effectively enhances the oscillatory spikes. It has also been observed that the oscillatory behaviour is in qualitative agreement with experimental observation as reported elsewhere for MOS structure of Hg_1–xCd_xTe. In addition, the corresponding results for inversion layers on parabolic semi-conductors are also obtained from the expressions derived.     

Auger-limited carrier lifetime in HgZnTe ambient temperature 10.6μm photoresistors

Photoconductive lifetime measurements have been carried out on both undoped and Cu doped p-type Hg_0.885Zn_0.115Te material prepared by a modified quench-anneal technique. An analysis of lifetime vs doping variations suggests that the Auger recombination mechanism is dominant. The experimental determination of the overlap integral has led to the value of 0.15. This fact and additional advantages (hardness, stronger chemical bonds, lower diffusion coefficients) make Hg_1−xZn_xTe extremely interesting for ambient temperature IR photoresistors.     

Influence of microwave treatment on the electrophysical characteristics of technically important semiconductors and surface-barrier structures

An investigation is made of changes in the electrophysical parameters of narrow-gap (Cd_xHg_1−x Te x=0.22–0.24) and wide-gap (gallium arsenide, indium and gallium phosphides) semiconductor materials and Schottky-barrier diode structures based on these materials, stimulated by microwave electromagnetic radiation. It is shown that the parameters of materials and device structures may be improved by defect gettering. An analysis is made of possible mechanisms for the interaction between microwave radiation and the objects being studied. Zh. Tekh. Fiz. 68, 49–53 (December 1998)     

Photosensitive structures using Hg1−xCdxTe solid solutions grown by molecular beam epitaxy

Results of a study of the parameters of Hg_1−xCd_xTe epitaxial structures produced by molecular beam epitaxy are presented. Results are given for measurements of the recombination and spectral properties and the noise properties of photosensitive elements have been studied. A high detectivity was obtained over a broad wavelength range. The parameters of MOS photodetector elements based on isotype n-Hg_1−xCd_xTe heterostructures with compositions x=0.2 and x=0.3 were estimated and compared with experimental data on the charge carrier accumulation time in MOS structures in the nonequilibrium depletion regine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 44–49, August, 1998.     

Optical and vibrational properties of CdxHg1-x-y ZnyTe solid solutions

The lattice dynamics of Cd_xHg_1-x-y Zn_yTe solid solutions is studied theoretically and experimentally. The frequencies of the basic optical phonons of Cd_xHg_1-x-y Zn_yTe are calculated in terms of a modified random-element isodisplacement model. As a result, all basic vibrations of the crystal lattice that substantially affect the optical properties of this material in the spectral region corresponding to one-phonon resonance are identified. The optical properties of epitaxial Cd_xHg_1-x-y Zn_yTe layers grown by liquid-phase epitaxy on Cd_1-x Zn_xTe substrates are studied. The calculated and experimental spectral dependences of the dielectric function of Cd_xHg_1-x-y Zn_yTe solid solutions of various compositions are compared at 295 and 78 K, and good agreement between them is reached. The additional lattice vibrations whose frequencies in the phonon density of states are lower than that of the HgTe mode are shown to be caused by the lattice defects of the Cd_xHg_1-x-y Zn_yTe solid solutions.