Maslyanchuk O. Mechanisms of Charge Transport and Photovoltaic Conversion in Detectors of Ionizing Radiation in Semi-Insulating Cadmium Telluride and its Alloys

The thesis deals with (i) the mechanisms of charge transport and photoelectric conversion in X- and gamma-radiation detectors based on CdTe and its alloys with the barrier structure and two ohmic contacts, (ii) the possibility of applications of CdZnTe and CdMnTe alloys in such detectors and (iii) the ascertainment of the causes of insufficient energy resolution in the spectra taken with the use of detectors with the Schottki diode and two ohmic contacts. (iii) A whole number of the features of the electrical characteristics of the crystals used in the X-and -detectors with an almost intrinsic conductivity and the deep energy levels in the bandgap (which are articularly important for the practice and not described in literature) have been revealed and explained. (iv) The properties of CdTe and CdZnTe crystals doped with element of III or V groups (In, Cl) have been substantiated analytically by the formation of self-compensated complexes for the first time. (v) The theoretical model that allows calculating the spectral distribution of the detection efficiency of X and gamma-rays in CdTe and CdZnTe crystals with Schottky diodes was proposed and substantiated. (vi) A correlation between the concentration of uncompensated impurities in crystals with the collection efficiency of photogenerated charge carriers in yhe detectors with Schottky diodes has been established. (vii) It is shown that thin layers (films) of CdTe with Schottky diode, which are not inferior to technologically sophisticated detectors on semi-insulating CdTe, can serve as an alternative to the existing X-ray image detectors based on selenium (a-Se).