Investigation of the effects of polishing and etching on the quality of Cd_1−xZn_xTe using spatial mapping techniques

Abstract

We examined the effects of polishing and etching on the structural and electrical properties of various high pressure Bridgman Cd_1−xZn_xTe (CZT) crystals using high resolution x-ray diffraction (HRXRD) and alpha particle mapping. Two etching solutions investigated are: (1) standard bromine-methanol solution, and (2) standard solution mixed with lactic acid. HRXRD, and in particular, triple axis x-ray diffraction (TAXRD) showed the effectiveness of the bromine-methanol etch in removing residual strain and damage from the CZT crystal. TAXRD mapping of a ∼5 cm² CZT crystal after etching resulted in a reduction of the average rocking curve full width at half maximum to 15 arc-sec (compared to 23 arc-sec for the “as-received”). Alpha particle mapping of the electron risetime and the pulse height spectrum, along with leakage current measurements, showed varying effects of the different etching solutions on the surface properties (and hence their influence on the electrical and detector properties). These preliminary results show the importance and the sensitivity of the overall detector properties on the surface preparation conditions of CZT crystals used as radiation detectors.