Lattice-mismatched In0.16Ga0.84As solar cells were grown on GaAs substrates using graded InxGa1−xAs buffer layers and homogenous In0.16Ga0.84As buffer layers. The indium composition x in the graded buffer changed continuously from 0 to 16%. Thermal cycle annealing (TCA) was performed after the growth of the graded buffer layers. The effects of TCA on the solar cell open-circuit voltage and quantum efficiency were investigated. The minority carrier lifetime was observed to increase in the p-type In0.16Ga0.84As layer after applying the TCA process. Electron-beam-induced current microscopy also showed a related reduction in dislocation density in the p-type In0.16Ga0.84As layer after TCA processing. Cross-sectional transmission electron microscopy performed on the graded buffer layer suggested that the strain present in the cell layers was reduced after the TCA process, implying that the TCA treatment promotes strain relaxation in the graded buffer layers.

Effects of Thermal Cycle Annealing on Reduction of Defect Density in Lattice-Mismatched InGaAs Solar Cells. T.Sasaki, K.Arafune, H.S.Lee, N.J.Ekins-Daukes, S.Tanaka, Y.Ohshita, M.Yamaguchi: Physica B, 2006, 376-377, 626-9