Phonons-defects interactions in CdTe

Publisher Website
Google Scholar
Abstract
A study of electrically inactive defects has been performed on CdTe single crystals by two different experimental techniques : • the low temperature thermal conductivity measurement. It has been used as a tool to study crystal defects, such as clusters, stacking faults or point defects ; • the X ray topography. It completes the first method in showing large aggregates (resolution ≃ 1 μm), dislocation arrays or structural defects. The following observations regarding the experimental results are worth noting. CdTe crystals (undoped, Cl or In doped) have been grown by melting zone or THM. Microprecipitates are found in all CdTe crystals. The concentration varies from 1014 up to 1015 cm-3 and the mean diameter reaches 100 Å or more. This concentration is independant on the doping level and on the crystal growth process. The presence of such a precipitation is probably associated with the chemical and thermal growth conditions of the crystals. The K( T) curves fit by the Callaway phenomenological model indicates a point defect concentration of about 1018 cm-3. The isotopical mass deviation introduces only a concentration of 7 × 1017 cm -3. The excess is ascribed to several origins such as nonstoichiometry in CdTe, doping, chemical impurities or VCd. In X-ray topography large precipitates appear only in crystals not intentionally doped and melting zone purified, or in CdTe : Cl. No correlation is found between large and micro precipitates. Dislocations with atmosphere appear also with a low concentration of about 104 cm-2