Proton irradiation damage for CuInSe2 solar cell material was investigated by using a piezoelectric photothermal spectroscopy from the viewpoint of non-radiative transition. Stoichiometric and Cu-rich thin film samples were grown on GaAs substrate for the measurements. Among the observed peaks at 1.01, 0.93 and 0.84eV for the proton irradiated samples at room temperature, two peaks at 1.01 and 0.93eV were attributed to the free exciton and the intrinsic defect level transitions, respectively. Since the peak at 0.84eV could not be observed for the sample before irradiation, it was considered that this peak was induced by the proton irradiation. The results indicated that the irradiation-induced Se vacancy played an important role in piezoelectric photothermal signal generation. Recovery of the irradiation damage was also observed by using this technique. Therefore, it was concluded that the piezoelectric photothermal spectroscopy technique was a powerful tool for studying the defect level in the irradiated semiconductor thin films.

Piezoelectric Photothermal Investigation of Proton Irradiation Induced Defects in CuInSe2 Epitaxial Films. Y.Akaki, N.Ohryoji, A.Fukuyama, K.Yoshino, S.Kawakita, M.Imaizumi, S.Niki, K.Sakurai, S.Ishizuka, T.Ohshima, T.Ikari: Thin Solid Films, 2005, 480-481, 250-3