ABSTRACT
The piezoelectric photoacoustic (PPA) spectra for the five CuInSe2 (CIS)/GaAs epitaxial layers with different Cu/In ratios of Cu/In=0.72, 0.82, 0.86, 1.04 and 1.79 were successfully observed at liquid nitrogen temperature. Three peaks which are due to intrinsic defect and bandgap of CIS and GaAs, are observed in each spectra. In the In-rich region, the bandgap energy of CIS decrease with decreasing Cu/In ratio. From the ratio of the peak intensity of bandgap of CIS and GaAs, we found that absorption coefficients of CIS epitaxial layers become large with decreasing Cu/In ratio in the In-rich region.
