Modification of surface state of CdZnTe crystals and contact formation

Different surface treatments such as chemical etching in bromine-containing solutions and nanosecond laser annealing were applied to provide the appropriate surface states of the CdZnTe (CZT) crystals prior to formation of metal-semiconductor contacts and electrode deposition. The effects of chemical etching and laser irradiation with different energy densities on the characteristics of the surface region of CZT solid solutions were studied. Depending on number and energy density of laser pulses and irradiation ambient conditions, photoelectric, electrical and optical properties of CZT crystals are changed and can be modified. Laser processing of CZT samples with the certain energy densities resulted in an increase in photosensitivity and transformation of photoconductivity (PC) spectrum profile. This was attributed to an increase in homogeneity in the crystal surface area and equalization of structural characteristics in the subsurface region and bulk of the samples. Irradiation of CZT crystals pre-coated with an electrode metal film allowed us to modify the I-V characteristics that can be employed in the fabrication of CZT-based X-ray and γ-ray detectors.