Effect of Fermi Level Motion on the Optical, ESR and Transport Properties of CuInSe2

The infrared (IR) absorption and ESR spectra of the CuInSe 2 crystals, grown by the normal freezing technique and subsequently annealed in various atmospheres, have been studied in connection with the annealing-induced motion of the Fermi level relative to the energy band edges. The degenerate n-type crystals exhibited a free-electron absorption, while the p-type crystals showed both an inter-valence-band and a free-hole absorption, from the analysis of which the energy positions of the Fermi level have been evaluated, and the electrical parameters of the respective crystals estimated; these results were then compared with the experimental results. In the ESR spectra the signals from iron residual impurity in both divalent and trivalent charged states, as well as the signals arising from native defects V Cu and In Cu , have been detected, the intensities of the ESR signals being dependent on the composition of the samples and the Fermi level position.