Optical properties and morphology of the opposite polar faces of CdTe(111) single crystals subjected to irradiation with nanosecond pulses of the second harmonic of a YAG:Nd laser in a wide range of energy densities have been studied by multiple-angle-of-incidence single-wavelength ellipsometry and atomic force microscopy. The ellipsometric data have been interpreted by the semi-infinite medium model and it is assumed that there are no films on the crystal surface. Also the one-layer model is applied and the crystal relief is considered as a top layer. The refraction n and absorption k indexes of the surface layer are calculated using the fundamental ellipsometric equation and method of thickness curves. Laser irradiation results in an increase in the refractive index of the CdTe surface layer due to laser-induced transformation of the surface structure and it is associated with enriching of the CdTe surface with tellurium. The surface morphology of the crystals is modified at higher laser pulse energy densities because of the beginning of melting of prominent irregularities and thin surface layer. The effects of irradiation with nanosecond laser pulses on the polar surfaces of CdTe(111) crystals are analyzed.

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The surface functional layers of commercial detectorgrade CdTe crystals are characterized after different surface treatments such as chemical polishing etching in bromine-containing solutions and laser annealing with nanosecond pulses of the second harmonic of a YAG:Nd laser. The effects of etching and laser irradiation with energy density near the melting threshold of CdTe on the optical properties of the CdTe crystal surface are studied using ellipsometry and photoluminescence (PL). The samples after storage in air are also investigated. The intrinsic emission band at 1.58 eV and broad dopant band peaked at 1.45 eV are observed in the PL spectra excited by a semiconductor laser with wavelength of 405 nm at 80 K. The low energy band is associated with carrier recombination at structural defects in the surface layer. The redistribution of the PL band intensities after chemical polishing is found and it is attributed to transformation of the point defect structure and defect formation in the surface region of CdTe. The laser treatment essentially changes the surface state and structure of the surface layer that can be used for effective modification of characteristics of the functional layers of CdTe crystals particularly band bending before formation of electrical contacts.

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