Optoelectrical properties of CuInSe2 thin films grown using hot wall epitaxy

Optoelectrical properties of CuInSe2 thin films grown using hot wall epitaxy

In this study, the photocurrent (PC) spectroscopy of undoped p-type CIS layers has been investigated at temperatures ranging from 10 to 293 K. Three peaks, A, B, and C, corresponded to the intrinsic transition from the valence band states of Γ7(A), Γ6(B), and Γ7(C) to the conduction band state of Γ6, respectively. Crystal field splitting and spin orbit splitting were found at 0.0059 and 0.2301 eV, respectively, and the temperature dependence of the optical band gap could be expressed using the empirical equation Eg(T)=Eg(0)-(8.57×10−4)T2/(T+129). But the behavior of the PC was different from that generally observed in other semiconductors: the PC intensities decreased with decreasing temperature. From the relation of log Jph vs 1/T, where Jph is the PC density, the dominant level was observed at the higher temperatures. We suggest that in undoped p-type CIS layers, the trapping center limits the PC signal due to native defects and impurities with decreasing temperature.

In this study, the photocurrent (PC) spectroscopy of undoped p-type CIS layers has been investigated at temperatures ranging from 10 to 293 K. Three peaks, A, B, and C, corresponded to the intrinsic transition from the valence band states of Γ7(A), Γ6(B), and Γ7(C) to the conduction band state of Γ6, respectively. Crystal field splitting and spin orbit splitting were found at 0.0059 and 0.2301 eV, respectively, and the temperature dependence of the optical band gap could be expressed using the empirical equation Eg(T)=Eg(0)-(8.57×10−4)T2/(T+129). But the behavior of the PC was different from that generally observed in other semiconductors: the PC intensities decreased with decreasing temperature. From the relation of log Jph vs 1/T, where Jph is the PC density, the dominant level was observed at the higher temperatures. We suggest that in undoped p-type CIS layers, the trapping center limits the PC signal due to native defects and impurities with decreasing temperature.