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.
The photon counting CdTe detector by using pulse rise height for high count rate detection was developed. The detector
can measure not only pulse rise height for energy estimation but also pulse rise time. The energy spectrum after
polarization in high bias voltage and before polarization in low bias voltage was so similar, but the pulse rise time was
difference. In this paper, we have compared polarization properties of M-p-n type CdTe diode and Schottky one. We will
estimate changing internal electric field by using this measurement.
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