Mechanism for Conversion of the Conductivity Type in Arsenic-Doped p-CdxHg1–xTe Subject to Ionic Etching

Based on an analysis of chemical diffusion of mercury in p-Cd _x Hg_1–x Te:As narrow-band solid solutions, a mechanism for conversion of the conductivity type upon ionic etching is suggested. It is shown that the n–p conversion of the conductivity in this case is due to the formation of a donor complex between arsenic in the Te sublattice and an interstitial Hg atom. Moreover, the electron concentration in the converted layer corresponds to the concentration of the implanted arsenic impurity. The theoretical results are confirmed by the experimental investigation of the electron concentration distribution over the n-layer of a p-Cd _x Hg_1–x Te:As epistructure converted upon ionic etching.     

The electrical properties of Cu2Te

The conductivity, Hall effect, and thermo-emf are reported for thin films and polycrystalline bulk specimens of Cu₂Te, which is found to be an impurity semiconductor whose forbidden band has a width of 0.9–1.0 eV. The compound dissociates on vacuum evaporation, so it is very difficult to produce thin films.I am indebted to Professor D. N. Naskedov for his interest and for valuable comments.     

Effect of thermal processing on the cluster and defect subsystems of Hg1−XMnXTe1−ySey crystals

Investigations of the effect of thermal processing in vapors of components (Se, Hg, and Te) on the magnetic susceptibility of Hg_1–XMn_XTe_1–ySe_y crystals which were conducted in the temperature interval T=77–360 K indicate an increase in uniformity with respect to cluster content during annealing in Se vapor, an increase in the paramagnetism of the samples when annealed in Hg vapor, and a significant degradation of the uniformity of the samples after thermal processing in Te vapor (up to second phase formation). The obtained results are explained by transformations in the cluster and defect subsystems of the crystals taking place during thermal processing.Chernovitskii State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 48–51, May, 1993.     

The effect of temperature and pressure on the heat conductivity of TlSbC<Stack><Subscript>2</Subscript><Superscript>VI</Superscript></Stack> (<Emphasis Type="Italic">C</Emphasis><Superscript>VI</Superscript> → S,Se, Te)

The effect of temperature and pressure on heat conductivity of ternary compounds TiSbC ₂^VI (C ^VI → S, Se, Te) in the solid and liquid states in a temperature range of 300–800 K, as well as under the pressure up to 0.35 GPa in a temperature range of 275–450 K, is studied. The dependence of heat conductivity on average atomic weight under the S → Se → Te transition is found. Analysis of the experimental data makes it possible to attribute TlSbS₂ to the class of substances exhibiting semiconductor-semiconductor melting behavior.     

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.     

Investigation of photoelectric and recombination characteristics of a CdHgTe optical mixer

An analysis is made of the heterodyne operation of a Cd_xHg_1–xTe (x=0.2) photoresistor detector. An allowance is made for the influence of the heterodyne power on the carrier lifetime in the case of the interband Auger recombination and recombination via Shockley-Read centers. It is found that the Auger recombination predominates at high heterodyne powers. It is shown that the pass band of the photodetector can be widened by increasing the heterodyne power. It is reported that the results of an experimental study of a Cd_xHg_1–x Te photoresistor detector are in good agreement with the calculations when the threshold sensitivity of the detector is limited by the thermal noise of the photoresistor.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 100–103, July, 1980.     

Mechanism for Conversion of the Type of Conductivity in p-Hg1–xCdxTe Crystals upon Bombardment by Low-Energy Ions

The main peculiarities of the p–n conversion of the type of conductivity in narrow-band p-Hg_1–x Cd _x Te solid solutions containing vacancies of mercury upon bombardment by low-energy ions are explained based on the traditional notions about the chemical diffusion of mercury. These peculiarities are related, on the one hand, to the features of the defect formation in Hg_0.8Cd_0.2Te (containing a small amount of high-mobility interstitial mercury atoms with a great amount of low-mobility vacancies) and, on the other hand, to the high concentrations of intrinsic electrons and holes efficiently screening the electric field of the defect layer. The high conversion rate realized upon ion bombardment, as compared to the conversion rate taking place upon annealing in mercury vapors, is due to the fact that nonequilibrium interstitial mercury atoms are produced in abundance near the surface of the crystal subject to bombardment. This effect depends substantially on the electric field appearing near the outer boundary of the converted layer; therefore, as the Hg content, and, hence, the width of the forbidden band, is increased, one should expect a noticeable decrease in p-n conversion rate.     

The structure of liquid In - Te and Tl - Te alloys

The atomic structure of liquid In—Te and Tl—Te alloys have been investigated as a function of composition and temperature by means of X-ray diffraction. The following features emerge from this experiment. The structure of liquid In—Te alloys is similar to that of pure Te in the range of composition from 35 to 100 at % Te. This implies that the structure of pure Te plays a significant role in these alloys. At the composition of In₂Te₃, the second peak near the region ofQ=3.2Å^–1 disappears with the increase of temperature. This corresponds to the breakdown of the electron localization based on the measurement of magnetic susceptibility. On the other hand, there is no substantial change in the structure of liquid Tl—Te alloys as the delocalization temperature of the electrons is approached.     

The performance of Hg1−x Zn x Te photodiodes

This paper considers the Hg_1–x Zn _x Te alloy system as a potential material for the fabrication of infrared photodiodes. The influence of different junction current components (diffusion, tunneling and depletion layer currents) on the R ₀ A product of n⁺-pHg_1–x Zn _x Te photodiodes is analysed. The upper theoretical limits of the R ₀ A product and detectivity are determined. Results of calculations are compared with experimental data reported by other authors and those measured in our laboratory. Preliminary results on related technology and the properties of Hg_1–x Zn _x Te prepared by the ion-etching technique are presented.     

The Rotational Spectrum of H2Te

In the present work, we study the spectrum of the H₂Te molecule in the submillimeter-wave and far infrared region. An important aim of this investigation is the further experimental characterization of the anomalous “four-fold cluster effect” exhibited by the rotational energy levels in the vibrational ground state of H₂Te. The spectrum in the region 90–472 GHz was measured with a source-modulated millimeter-wave spectrometer and that between 600 and 1600 GHz with a far-infrared sideband spectrometer. The far infrared spectrum from 30 to 360 cm⁻¹was measured with a Bruker IFS 120 HR interferometer attached to a 3 m long cell. We have assigned 224 submillimeter-wave lines and 1695 FIR lines. These observed data were supplemented by a large number of ground state combination differences derived from rotation–vibration bands of H₂Te, and the resulting large data set was analyzed by means of a modified Watson Hamiltonian. Accurate sets of rotational and centrifugal distortion constants for all eight tellurium isotopomers were obtained.     

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.     

Atomic and electronic structure formation at the metal-Cd1−xMnxTe interface

Atomic and electronic structure modification of a metal-Cd_1−xMn_xTe interface is achieved using selective etching of the Cd_1−xMn_xTe surface (x=0, 0.34) and Cd adsorption. It is revealed that Te, TeO₂, Mn₃O₄, and CdTeO₃ are formed at the Cd_1−xMn_xTe surface etched in Br₂ solution. Te and Cd_1−xMn_xTe produce TeCd_1−xMn_xTe heterojunctions, the salient features of which are nearly symmetric nonlinear I-V characteristics. At the Cd_1−xMn_xTe surface with adsorbed Cd, CdTe might form, resulting in a CdTe-Cd_1−xMn_xTe heterojunction. The metal-CdTe-Cd_1−xMn_xTe microstructure is characterized by a nonlinear dependence of current on voltage and rectifying behaviour. The results obtained give deep insight into electronic processes in metal-Cd_1−xMn_xTe microstructures.     

Effect of bismuth on the electrical properties of Pb0.8Sn0.2Te thin films

D.C. conductivity and Hall coefficient studies were made on bismuth doped Pb_0.8Sn_0.2Te thin films in the temperature range 77–300 K. Hall coefficient and Hall mobility are found to decrease with the increase in doping density of bismuth. Films doped with even 0.3 at.% Bi changed fromp-type ton-type due to the donor action of bismuth in these films. Analysis of mobility-temperature data revealed that the lattice and defect scattering mechanisms are predominant in these films. Defect limited mobility is calculated for all the films and it is found to decrease with increase in doping concentration of bismuth suggesting the increase in defect density.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.     

Effect of tellurium on electrical and structural properties of sintered silicon nitride ceramics

The effects of tellurium (Te) additives on electrical conductivity, dielectric constant and structural properties of sintered silicon nitride ceramics have been studied. Different amounts of Te (10% and 20%) were added as sintering additives to silicon nitride ceramic powders and sintering was performed. Microstructure and composition were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrical conductivity and dielectric constant (ε′) increase exponentially with temperature greater than 800 K. The electrical conductivity and dielectric constant increase but activation energy decreases from 0.72 to 0.33 eV with the increase of Te concentration. However, the conductivity increases five orders of magnitude at the concentration of 10% of Te in Si₃N₄. As the Te concentration increases the sintered silicon nitride ceramics become denser. These types of samples can be used as high temperature semiconducting materials.     

Electron–hole symmetry and spin–orbit splitting in IV–VI asymmetric quantum wells

It is shown that, due to the electron–hole symmetry of the fundamental gap of the lead–salts (PbTe, PbSe and PbS), the Rashba spin splitting in their flat band asymmetric quantum wells is much reduced with the usual equal conduction and valence band-offsets. Different from the III–V case, we find that the important structure inversion asymmetry for the Rashba splitting in IV–VI quantum wells with different left and right barriers is not a material property (i.e., barrier height, effective mass or band gap) but results from the band alignment. This is shown by specific envelope function calculations of the spin-dependent subband structure of Pb_1−xEu_xTe/PbTe/Pb_1−yEu_yTe asymmetric quantum wells (x≠y), based on a simple but accurate four-band kp model for the bulk band structure near the gap, which takes into account band anisotropy, nonparabolicity and multi-valley effects.     

Dc and ac electrical conductivity of bulk CdSexTe1−x (0x0.4)

Measurements of the dc and ac conductivity were made for polycrystalline CdSe_xTe_1−x (0x0.4) at various frequencies (0.1–100 kHz) and at various temperatures (293–413 K). The temperature dependence of the dc conductivity was measured in the temperature range (293–413 K). It was found that the obtained dc activation energy for the investigated compositions decrease with the increase of Se content. The ac conductivity is found to be frequency and temperature dependent and obeys the Aω^s law, where s decreases with the increase of temperature. The ac conductivity of these compositions are explained on the basis of the correlated barrier hopping model.     

Electrical conductivity improvement of strontium titanate doped lead vanadate glasses by nanocrystallization

The structural and electrical conductivity (σ) of annealed SrTiO₃–PbO₂–V₂O₅ glasses were studied. The annealing of initially glass samples leads to formation of nanocrystalline grains embedded in the glassy matrix. XRD patterns of the glass–ceramic samples show that nanocrystals were embedded in the glassy matrix with an average grain size of 32 nm. The glass–ceramic nanocrystals obtained by annealing at temperatures close to the crystallization temperature T_c exhibit enhancement of electrical conductivity up to four orders of magnitude than initially glasses. The enhancement of the electrical conductivity due to annealing was attributed to two interdependent factors: (i) an increase of concentration of V⁴⁺–V⁵⁺ pairs; and (ii) formation of defective, well-conducting regions along the glass–crystallites interfaces. From the conductivity temperature relation, it was found that small polaron hopping model was applicable at temperature above θ_D/2 (θ_D, the Debye temperature). The electrical conduction at T >θ_D/2 was due to non-adiabatic small polaron hopping (SPH) of electrons between vanadium ions. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with glass composition.     

Near-infrared intersubband absorption in (CdS/ZnSe)/BeTe type-II super-lattices grown on GaAs substrate by MBE

We study the dependence of absorption wavelength on the well width in the (CdS/ZnSe)/BeTe super-lattices(SL). With well-width reduction, the wavelength decreases from 1.795 to 1.57 μm. Structural properties, strain state and interface composition are determined via XRD measurement. A (CdS/ZnSe)/Be_xMg_1−xTe structure is prepared and XRD reveals the average lattice constant match to GaAs substrate. TEM reveals that numerous stacking faults exist in the (CdS/ZnSe)/BeTe structure, and stacking faults are completely suppressed in (CdS/ZnSe)/Be_xMg_1−xTe SLs. Intersubband transition down to 1.535–1.55 μm have been observed in SLs.     

Investigation of the total conductivity of heterolasers with a strip contact with reverse bias

The electrical properties of DGS lasers with a strip contact on the basis of Al_xGa_1–xAs with reverse bias, including the breakdown domain, are investigated experimentally. It is shown that the dependence of the barrier capacitance on the voltage is described well by the relationship C_b = C_o/(1– V/V_k)^1/m, where C_o = (50–110) pF and m = 2.0–2.7. The capacitance for zero bias C_o depends weakly on the frequency in the range 660 kHz–60 MHz. The active conductivity for V = 0 increases by approximately an order as the frequency changes from 15–60 MHz. The dependence of the active and reactive components of the total laser conductivity on the current is investigated at fixed frequencies in the range mentioned. The weak dependence of the reactive component on the current is noted in the breakdown regime associated with stabilization of the reverse voltage on the laser. Possible physical mechanisms responsible for the kind of characteristics obtained are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 52–56, November, 1983.