Surface processing of CdZnTe crystals

The Cd 1-x Zn x Te ( x = 0.1) crystals from two different manufacturers were studied by photoconductivity (PC) measurements. The samples 1 and 2 were subjected to chemical etching and irradiation with nanosecond laser pulses. The IR transmittance spectra of the crystals before and after laser irradiation were also monitored. The PC spectrum of the sample 1 had a typical one-band shape while the spectrum of the sample 2 exhibited two bands roughly corresponding to the bandgaps of CdTe and Cd 1-x Zn x Te that could be attributed to inhomogeneities in the surface region of the crystal. The positions of the maximum and red edge of the PC spectra did not correspond to the component compositions x in the bulk of Cd 0.9 Zn 0.1 Te crystals, however chemical polishing etching of the samples in a brominemethanol solution or/and laser irradiation led to this correspondence. Moreover, depending of laser pulse energy density, irradiation of Cd 1-x Zn x Te crystals resulted in a short-wavelength shift of the PC spectra, transformation of two bands to one in the case of the sample 2, and an increase in the photosensitivity of the semiconductor. The laser processing provided equalization of parameters in the surface and bulk regions.