The photorefractive characteristics of Ti-doped CdTe semi-insulating crystals were measured. Additional optical and photoelectric measurement confirmed that titanium has advantages over other dopants and that this material has better characteristics for potential applications. The high optical holographic gain coefficient, Γ≈0.60 cm−1, low background absorption, kb≈0.2 cm−1, high optical quality and homogeneity, and almost monopolar (electronic) photoconductivity show that these materials can be effectively used for both optical and photoelectric applications in the near infrared region. Studies of the optical absorption and photodiffusion current made it possible to determine the nature and energy structure of impurity and intrinsic defects as well as to establish their role in the photorefractive effect. It is shown that the excited impurity T14(F) state is in resonance with the conduction band. As a result, autoionization of electrons to the conduction band under laser excitation takes place. An energy-level diagram, both of impurity and intrinsic defects, in the CdTe:Ti crystals was constructed.

The nature and the energy structure of impurity and intrinsic defects, including the formation of anisotropic impurity centres, are determined in V-doped semi-insulating Cd 1−x Hg x Te (x 0.037) crystals which were grown by the Bridgman technique for the first time. From detailed analysis of the spectral dependence of the photodiffusion current data obtained for the different directions of light propagation in crystals as well as the impurity absorption spectra, we established that for the investigated crystals anisotropic V 2+ and V 3+ centres are formed. Two mechanisms of the electron photogeneration from the ground impurity state to the conduction band (direct photoionization and auto-ionization from the excited state V 2+ ions) are established. It is shown that the efficacy of the auto-ionization of electrons depends on the position of the excited state relative to the conduction band bottom. The photoinduced impurity centres are formed as a result of the illumination of the crystals with the light with energy about 1.50 eV. The nature and photoionization energy of these photoinduced centres are determined. The scheme of the impurity and intrinsic defects energy levels in the energy gap of the investigated crystals is presented.

Vanadium-doped semi-insulating Cd1−xHgxTe (x < 0.05) n-type crystals were grown by the Bridgman technique for the first time. Studies were carried out of the low-temperature optical and photoelectric properties of Cd1−xHgxTe (x = 0.014), which provided information on the deep anisotropic impurity centres and intrinsic defects. The nature and the position of their energy levels with respect to the crystal energy band were determined. It was shown that for the investigated crystals there are two photogeneration mechanisms of electrons from deep impurity levels: the auto-ionization of electrons from the discrete state, which is in resonance with the conduction band, and their direct photoionization. It was found that the photosensitivity region for Cd0.986Hg0.014Te:V crystals is about 1.3 μ m.

The results of a study of the structural and magnetic properties of single-crystal samples of the diluted magnetic semiconductor Hg1−xCrxSe with different concentrations of chromium ions (0&lt;x⩽0.07) in the temperature interval 50–300 K are reported. It is found that the boundary of the existence region of the homogeneous solid solution lies at chromium concentrations x&lt;0.05. In samples with x⩾0.05 the sharp growth of the magnetic susceptibility in the region of the phase transition temperature is due not only to a transition to a phase similar to a spin-glass phase, which is observed in all the samples studied, but also to a ferromagnetic contribution from ferromagnetic inclusions of HgCr2Se4 and CrSe in those samples.

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