The electrical characteristics of x-ray and γ -ray detectors with Schottky diodes on the basis of CdTe crystals of n-type conductivity with a resistivity of 10 2 -10 3 cm (300 K) are investigated. The necessary parameters of the diode structures are determined to interpret the detection characteristics of the detectors. The dependences of the charge-collection efficiency in the detectors on the carrier lifetime and concentration of uncompensated donors are obtained and the conditions for the total collection of charges generated by the photon absorption are established. Taking into account drift and diffusion photocurrent components, the spectral distribution of the quantum detection efficiency is calculated. The comparative analysis of the detection efficiency of Schottky diodes based on low-resistivity p-CdTe and n-CdTe shows the advantages of the latter, especially in a low x-ray energy region.

The defect structure of donor-doped Te-rich CdTe is studied theoretically within quasi-chemical formalism and experimentally in heavily In-doped CdTe by in situ high temperature galvanomagnetic measurements in the temperature interval 900 -200 °C. The experimental data are evaluated within defect model optimized to recent high temperature experiments and assuming doping-induced band gap renormalization. We show that a proper thermal treatment can be conveniently used for the optimization of room temperature electric properties and for a preparation of the semi-insulating detector grade material with a deep level doping below the limit 10 13 cm -3 demanded in the detector industry.

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Self-focusing of 1aser beams is observed in Cd0.5Mn 0. 5 Τe at room temperature. The far-field patterns of laser beam after passing through the cad-mium manganese telluride crystal are investigated. The values of focal length as well as the absorption coefficient were measured as a function of intensity of laser radiation. From these measurements the values of nonlinear refrac-tive index for Cd0.5Mn0.5Te are determined. The results indicate that the self-focusing observed in Cd 1-x ΜnxTe is due to a thermally induced change in refractive index. PACS numbers: 42.65.Jx A well-known third-order nonlinear optical effect of great interest is the phenomenon of self-focusing of light. Self-focusing may occur when the refractive index of the nonlinear medium increases with the beam intensity, n = n0 + Δn, where Δn is the laser induced refractive index. and n 0 is the index of refraction for low intensity light. One of the most important physical mechanism responsible for Δn in semi-conduction is heating by CW laser beam with photon energies close to the band gap energy. It leads to dispersive nonlinearity induced by a shift of the band gap energy. In case of a laser beam with a Gaussian transverse profile propagating into the semiconductor with dn/dT > 0, the central part of the beam sees a larger refractive index than the edge. Consequently, the beam is focused by itself. Dis-persive nonlinearisty induced by a thermal shift of the band gap energy has been studied in several semiconductors [1]. In this paper the investigations of self-focusing of laser beam in Cd0.5Mn0.5Te is reported. It should be noticed that in Cd1-xMnxTe crystals with x > 0.5 the fundamental absorption is obscured by transitions within Mn++ ions [2]: Therefore,

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