Characterization of CdTe crystals by chemical etching and cathodoluminescence measurements

A double etch process has been developed, based on the well-known Inoue etch solution, in order to achieve greater control over the generation of etch pits on CdTe crystals. A comparison of the resulting etch patterns with those generated by applying another well-known (Nakagawa) etchant suggests an attacking of extended crystal defects by the former and a more sensitive etching of isdlocation sites by the latter etchant. Since such extended crystal defects are correlated with precipitates in the crystals, the etching procedure allows a major excess concentrations of Cd or Te to be spatially resolved. The character of these precipitates was measured by cathodoluminescence and was found to be spotty for CdTe crystals grown under high Cd excess and more threaded when grown under high Te excess in the melt.