Unique features of the magnetic susceptibility of Hg1−xMnxTe1−ySey

The magnetic susceptibility of the new semimagnetic solid solutions Hg_1–xMn_xTe_1–ySe_y (0Mn = f(T) are caused by the presence within the specimen of Mn-Te-Mn-Te, Mn-Se-Mn-Se, and Mn-Te-Mn-Se type clusters, in which indirect exchange action of an antiferromagnetic character occurs among the Mn atoms by means of the Te or Se atoms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 60–62, April, 1991.     

Field inversion of the sign of the hall coefficient in Hg1−xMnxTe1−ySey

In the temperature range T=77–300 K and H1–18 kOe, the dependence of the Hall coefficient (R_H) of crystals of Hg_1–xMn_xTe_1–ySe_y (0H=f(H), as well as the inversion of the sign of R_H as H increases for Hg_1–xMn_xTe_1–ySe_y (x0.1 and y=0.05) are explained by the presence in the samples of three types of charge carriers: holes, and heavy and light electrons.Chernovitskii University. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 4, pp. 11–14, April, 1994.     

Phase differences between quantum oscillations of the magnetoresistance and the hall effect in Hg1−xMnxTe and Hg1−xCdxTe

A Landau-level broadening-dependent phase shift has been observed between the Shubnikovde Haas oscillations of the magnetoresistance and the Hall effect in a series of Hg_1−xMn_xTe and Hg_1−xCd_xTe samples. The phase shift varies between 0 and 90° and appears not to be influenced by the exchange interaction between the Mn²⁺ ions and the carriers. The results are in good agreement with the theoretical predictions for short range scattering potentials.     

First principle electronic structure calculations of ternary alloys Hg1−xMnxTe in zinc-blende structure

We have investigated the structural, electronic, magnetic and optical properties of Hg_1?xMn_xTe in the zinc-blende phase for 0≤x≤1. The calculations were performed by using the full potential linearized augmented plane wave plus local orbitals method within the framework of the density functional theory. The lattice constants of Hg_1?xMn_xTe at different Mn concentrations exhibit Vegard's law perfectly. For spin-up channel the Mn 3d bands are occupied and mixed with the Te 5p bands whereas for spin-down channel the Mn 3d bands are unoccupied. The values of the p–d exchange splitting energy, ?_x(pd) as produced by the Mn 3d states are given. The contribution of the valence band and the conduction band in the process of exchange and splitting is described by the exchange coupling constants N₀α and N₀β. Due to p–d hybridization the magnetic moment of the Mn atom reduces, which results in small local magnetic moments on the non-magnetic Hg and Te sites. The potential applications of Hg_1?xMn_xTe in infrared device have been discussed on the basis of its optical properties.     

The realization of ion-implanted Hg1−xCdxTe photovoltaic arrays

A review of the main aspects of the realization of PV Hg_1−xCd_xTe arrays is presented. Results obtained on coating this material are reported and related to the carrier concentration of the bulk. Changes in the electrical properties, produced by ion implantation, are also reported and discussed.     

Spinglass behaviour of Zn1−xMnxSe and Zn1−xMnxTe semimagnetic semiconductors

The magnetic susceptibility of Zn_1−xMn_xSe (0.02 ≤ × ≤ 0.53) and Zn_1−xMn_xTe (0.07 ≤ × ≤ 0.21) was investigated in the temperature range 10 mK < T < 40 K. A paramagnetic spinglass transition was observed in the whole concentration range. The concentration dependence of the freezing temperature T_f was found to be compatible with a radial dependence of the exchange interaction between manganese ions of the type J(R) ∝ R^−6.8. It appears from the available data that this radial dependence is rather universal for all II–VI wide gap semimagnetic semiconductors. A comparison is also made with other semimagnetic semiconductors and the physical exchange mechanism is discussed.     

Analysis of the R0A product in n+-p Hg1−xCdxTe photodiodes

The influence of different junction current components (diffusion current for radiative and Auger 7 recombination mechanisms, tunneling and depletion layer currents) on the R₀A product of n⁺-p -Hg_1−xCd_xTe photodiodes is considered. The considerations are carried out for the 77–300 K temperature region and 1–15 μm cutoff wavelength. Optimum doping concentrations in the p-type region of n⁺-p abrupt junctions are determined, taking into account the influence of the tunneling current and of a fixed surface charge density of the junction passivation layer. Results of calculations are compared with experimental data reported by many authors. An attempt is made to explain the discrepancy between theoretical calculations and experimental data.     

The behavior of Shubinikov-de Haas oscillations in Hg1−x−yCdxMnyTe alloys

The transverse and longitudinal magnetoresistance are measured on a quaternary semimagnetic semiconductor, n-type Hg_1−x−yCd_xMn_yTe with 0.01 < x < 0.23 and y ≈ 0.14, at different temperatures. The peaks of the Landau-spin states are assigned using the selection rules already developed for HgCdTe. The Landau-spin states are modified by an exchange interaction between the Mn²⁺ ions localized spin and the band electrons, thus it becomes possible to compare directly the extent of the spin modification between the negative gap side and the open gap side of the new alloys.     

Optical properties of Hg1−xCdxTe

Optical properties of Hg_1−xCd_xTe are summarized in this study. Based on Penn-like models, the Moss relation and the Wemple and DiDomenico approach, calculations of energy gap, plasmon energy, Fermi energy, oscillator strength and electronic polarizability have been made. Comparisons are made with the data available in the literature. Details of the dependency of the properties on composition are presented.     

Temperature dependent photoconductivity and photoluminescence of Cd1 − xMnxTe

Photoconductivity (PC) and Photoluminescence (PL) studies of Cd_{1 − x}Mn_xTe are reported in the ranges of composition 0.15 ⪅ x ⪅ 0.40 and temperature 10 ⪅ T ⪅ 300 K. The results of this study show that p-d transitions make an important contribution to the optical properties of Cd_{1 − x}Mn_xTe in the above range of compositions. Based on UPS and an estimate of the spin-flip energy for the Mn d electrons in Cd_{1 − x}Mn_xTe from literature data we place the centers of the Mn d↑ and Mn d↓ bands contributing to the photoemission and p-d transition processes at -3.5 eV and +2.0 eV, respectively, relative to the Γ₈ valence band edge. Strong changes in both the PL and PC spectra are observed when the Γ₆ conduction band edge shifts through the Mn 3d↓ levels. This explains the specific temperature dependence of the PC for x = 0.32 and the strong increase in the normalized intensity of the PL band at 2.0 eV at x ⪆ 0.35. The shift in the binding energy of the excitonic contribution to the PC with temperature agrees well with the model of Golnik on interactions of the excitons with the Mn²⁺ spins.     

Photoresponse of Hg1−xCdxTe n-channel MISFETs

Photogenerated currents at 77 K, when the Semitransparent gate of an Hg_1−xCd_xTe(x = 0.205) n-channel MISFET is illuminated with IR radiation of varying intensities, have been evaluated theoretically. Two different processes of excitation are considered, namely, electron-hole pair excitation across the bandgap in the depletion layer of the field-induced junction and excitation of carriers to the conduction band from surface states lying near the middle of the bandgap. The photocurrent, in this case, is primarily due to the latter process. For the sake of comparison, the drain-source current without illumination has also been calculated as a function of the gate voltage.     

The refractive index dispersion of Hg1−xCdxTe by infrared spectroscopic ellipsometry

The refractive indices of Hg_1−xCd_xTe (x=0.276, 0.309, and 0.378) bulk samples in the region below, in, and above the fundamental band gap have been measured by infrared spectroscopic ellipsometry at room temperature. A refractive index peak, in which the corresponding energy equals approximately the band gap energy, is observed for each refractive index spectrum with different compositions. Above the band gap, the refractive index drops quickly near the gap, then decreases slowly as photon energy increases. The refractive index n above the band gap is found to follow the Sellmeier dispersion relationship n²(λ)=A+B/λ²+C/λ⁴+D/λ⁶ as a function of the wavelength of light λ.     

Characterization of flash evaporated Hg1−xZnxTe films

Results of structural, optical and electrical properties of flash-evaporated Hg_1−xZn_xTe films. in the composition range 0.08 ⩽ x ⩽ 1, show that the films are formed by alloying HgTe and ZnTe. The optical band gap of these films increases from 0.04 to 2.26 eV with an increase in Zn concentration from 0.08 to 1.0. The band gap variation is not linear but shows a “bowing effect” familiar to pseudobinary solid solutions. An increase in resistivity with an increase in the substrate temperature can be related to larger grain size at the higher substrate temperatures in these p-type films. The films exhibit higher conductivity for the Hg-rich films which decreases linearly as the Zn concentration is increased.     

Properties of Hg implanted Hg1−x Cd x Te infrared detectors

Experimental performance parameters of Hg implanted Hg_1?x Cd _x Te photovoltaic detectors are analyzed. At 77K, for 8–14 μm band, a comparison is made between performances and theoretical ultimate diffusion limits in low frequency direct detection. Experimental features are well-explained by a model based on the Auger band-to-band process for carrier recombination. Peak detectivities exceeding 10¹¹ cm Hz^1/2W^?1, external quantum efficiencies as high as 90%, and zero-bias resistance-area products better than 1 Ω·cm² have been achieved in devices with 12 μm cutoff wavelengths. In the 3–5 μm band performances are far from the diffusion limit. Notwithstanding, at 77K zero-bias resistance-area products are better than 10⁴Ω·cm² and detectivities of the order of 10¹² cm Hz^1/2W^?1 were observed at 5 μm. Predominant generation-recombination contribution are present at room temperature in 1–1.3 μm photodiodes whose detectivities, primarily limited by the Johnson noise, at 1.3 μm are higher than 10¹¹ cm Hz^1/2W^?1 at 300 K. The high frequency response of the photodiodes is also discussed. Response times as low as 0.5 ns are reached despite some limitations arising from the implanted layer sheet resistance.     

The influence of doping on ultimate performance of photodiodes for the 8–14 μm spectral range

The zero-bias resistance-area product (R_oA) of LN₂ temperature Cd_xHg_1−xTe 8–14 μm range photodiodes has been calculated. The influence of the types: the Auger and the radiative recombination in p- and n-type regions was taken into account.It was shown that the photodiode ultimate performance is determined by the Auger 7 recombination in p-type material. The ultimate value of (R_oA) is about 8 Ω cm² and it is much lower than calculated in recent works.     

Far-infrared detection with Hg1−xCdxTe

We report detection in liquid He cooled n−Hg_1−xCd_xCd_xTe at wavelengths between 140 and 1200 μm. With the mole fraction, x, of Cd <0.4m the alloy behaves as an electron bolometer with similar detectivity, but much improved bandwidth, compared with n-InSb. With x > 0.48 the detection process is extrinsic photoconductivity with an energy gap of a few meV. Lattice absorption severely limits detection in the wavelength range 220–340 μm.     

Topographic methods of studying defects in Hg1−xCdxTe crystals

In this paper, three topographic methods of studying defects in Hg_1−xCd_xTe crystals are described: the back-reflection method with a “whiter” beam, the scanning-reflection method with monochromatic radiation, and the glancing-incidence method with a “white” beam. Unique results obtained by these methods are shown: topographs as a referable criterion of various defects are laid down and explanation of the topographs is carried out theoretically. A set of topographs with reversed contrasts is made and the microorientation differences among the mosaic blocks are determined. Topographs of the intensive strain field in the core region of ingots prepared by the quench-recrystallization method are made and the mechanism of crystal growth is interpreted according to these topographs. In addition, typical topographs made by the three methods respectively, are shown.