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 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.

No abstract

No abstract

No abstract