An investigation was made, of the predominant intrinsic defect levels, by using temperature- and excitation-dependent steady-state photoluminescence methods. The polycrystalline thin films were prepared via the rapid thermal treatment of metallic alloys in H2Se-Ar. Attention was focussed on the effect of post-growth treatment (in Ar-H2 or O2) upon the defect structure. It was found that the photoluminescence spectra of slightly In-rich as-grown films were dominated by a donor-acceptor pair transition at 0.92eV. The defect levels were attributed to VCu and VSe, and their activation energies were determined as being 0.045 and 0.095eV, respectively. Post-growth treatment in Ar-H2 resulted in a shift of these peaks to higher energies, and to a significant increase in the intensity. On the other hand, annealing in O2 resulted in a shift of the peak to lower energies and to a marked reduction in intensity as compared with as-grown samples. The effects were found to be reversible. The changes in the photoluminescence spectra due to O or H annealing were explained by a change in the density of VSe defects. This was explained in terms of a model in which O could occupy a VSe site, due to coordinationally unsaturated In at the grain boundaries. The VSe concentration, and therefore device quality, of CuInSe2 thin films could therefore be controlled by post-growth annealing, or during growth.

Control and Passivation of VSe Defect Levels in H2Se-Selenized CuInSe2 Thin Films J.H.Schön, V.Alberts, E.Bucher: Semiconductor Science and Technology, 1999, 14[7], 657-9