Defect chemistry of CuInS 2, investigated by electrical measurements and Mössbauer spectroscopy

Abstract

Electrical measurements are performed on CuInS 2 single crystals (grown via chemical vapour transport), which were annealed under well defined conditions of molecularity and stoichiometry on four different positions of the CuInS 2 phase boundary. In this way two acceptor levels are detected, viz. at 0.10 eV in In-rich material and at 0.15 eV in Cu-rich material. The first is ascribed to V cu, the latter to V In or Cu In. Also a donor level at 0.035 eV is observed, which is assigned to V s or In cu as most likely defects. The incorporation of iron, which is by far the most important impurity as revealed by spectrochemical analysis (concentration about 5 × 10 18 cm −3), was studied by means of Mössbauer spectroscopy. Irrespective of the molecularity and the stoichiometry iron appeared to be incorporated as Fe 2+ on both Cu and In sites in a concentration ratio of roughly 3:1.