An analysis of temperature-dependent absorption and photocurrent spectra in BaAl2Se4 layers

作者：Hong K J^*; Jeong T S; Youn C J; Moon J D

来源：Journal of Applied Physics, 2015, 117(16): 165704.

DOI：10.1063/1.4918725

The temperature-dependent photoresponse behavior of BaAl2Se4 layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by E-g(T) = E-g(0) - 4.39 x 10(-4)T(2)/(T+250), where E-g(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Gamma(3)(A), Gamma(4)(B), and Gamma(5)(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Gamma(3)(A), Gamma(4)(B), and Gamma(5)(C) to the conduction band state of Gamma(1), respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log J(ph) versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl2Se4 layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

• 出版日期2015-4-28