Photocurrent-response study for valence-band splitting and band-gap energy of photoconductive AgGaSe2 layers

摘要

Photoconductive AgGaSe2 (AGS) layers were epitaxially grown along the <112> direction onto GaAs (100) substrates using the hot wall epitaxy method. By measuring the photocurrent (PC) spectra, three peaks were observed at the temperature range 10-100 K. These peaks are caused by the band-to-band transition from the valence-band state of Γ7(A),Γ6(B), and Γ7(C) to the conduction-band state of T6, respectively. Thus, the crystal-field splitting and the spin-orbit splitting were estimated to be 0.251 and 0.310 eV, respectively. However, a good agreement between optical absorption and PC-peak energy was acquired. The band-gap variation as a function of temperature on AGS was well fitted by E_g(T) = 1.950 - 8.37 x 10~4 T~2/(T+ 224). The band-gap energy of AGS obtained at 293 K was extracted out to be 1.811 eV by means of the PC experiment and optical absorption.