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Piezoelectric Photo thermal and Surface Photo voltage Spectra of Chalcopyrite CuGaSe/sub 2/ Epitaxial Layers fabricated on semi-insulating GaAs

Piezoelectric photothermal spectroscopy (PPTS) measurement for CuGaSe2 (CGS)/GaAs epitaxial layer (Cu/Ga=1.09) grown by molecular beam epitaxy (MBE) were carried out at low temperature (80K). The surface photovoltage (SPV) measurement was also done for comparison. Photo-induced change of the EL2 defect levels from normal to metastable states in the GaAs substrate drastically change the shape of the PPT spectra. Since no change was observed in the SPV spectra, we consider that the PPT method is effective for investigating the nonradiative electron recombination