Photoluminescence and optical properties of the surface functional layer of detector-grade Cl-compensated
semiconductor CdTe(111) single crystals modified by chemical etching and nanosecond laser processing have been
studied. A bromine-methanol solution was used for polishing etching and nanosecond pulses of the second harmonic of
YAG:Nd laser was applied as a radiation source. The photoluminescence spectra were excited at 80 K by an argon-ion
laser with wavelength of 488 nm. The intrinsic emission band at 1.56 eV and broad defect band peaked at 1.45 eV were
observed in the spectra before and after chemical and laser processing of CdTe crystals. The emission between 1.4-1.5
eV was associated with carrier recombination at defects in the surface region, so called the band of surface states. The
optical parameters were determined using an ellipsometer with laser wavelength of 632.8 nm. Refraction n and
absorption k indices were calculated within model of a homogeneous absorbing surface layer upon an absorbing
substrate. An increase in n and k was observed at laser irradiation with energy density near or higher than the CdTe
melting threshold that was attributed to an increase in volume fraction of Te in the surface region of the crystal. A
decrease in the emission intensity at 1.45 eV was evidence of a reduction of the surface impurity contribution to the
spectrum as a result of chemical etching. A rise of this band after irradiation was due of formation of point defects and
dislocations in a surface layer of the crystal.
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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