CdIn2S4 (110) films were grown on semi-insulating GaAs (100) by a hot wall epitaxy method. Using photocurrent (PC) measurements, the PC spectra in the temperature range of 30 to 10 K appeared as three peaks in the short wavelength region. It was found that three peaks, A-, B-, and C-excitons, correspond to the intrinsic transition from the valence band states of Gamma(4)(z), Gamma(5)(x), and Gamma(5)(y) to the exciton below the conduction band state of Gamma(1)(s), respectively. A 0.122 eV crystal field splitting and the 0.017 eV spin orbit splitting were obtained. Thus, the temperature dependence of the optical band gap obtained from the PC measurements was well described by E-g(T)=2.7116 eV-(7.65x10(-4) eV/K)T-2/(425+T). However, the behavior of the PC was different from that generally observed in other semiconductors. The PC intensities decreased with decreasing temperature. This phenomenon had ever been reported in a PC experiment on bulks crystals grown by the Bridgman method. From the relation of log J(ph) vs 1/T, where J(ph) is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. Consequently, the trapping centers due to native defects in the CdIn2S4 film were suggested to be the cause of the decrease in the PC signal with decreasing temperature.

Keywords: photocurrent; band-gap; valence band splitting; hot wall epitaxy; ternary compounds