Behavior of temperature-dependent photoresponse in unintentional p-type BaIn2Se4 layers through photocurrent spectroscopy

Abstract

Temperature-dependent photocurrent (PC) behavior of unintentional p-type BaIn2Se4 layers grown through the hot wall epitaxy method has been investigated. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ3(A), Γ4(B), and Γ5(C) to the conduction band state of Γ1, respectively. The interval on the valence band splitting of the crystal field and the spin orbit splitting was observed to be 0.0903 and 0.1507 eV, respectively. The temperature dependence of the optical bandgap energy could be well expressed by using Varshni's formula: Eg(T) = Eg(0) − αT2/(β + T), where α and β are taken to be 4.96 × 10−3 eV/K and 554 K, respectively. Also, the Eg(0) was estimated to be 2.6262, 2.7165, and 2.8672 eV at the valence band states of Γ3(A), Γ4(B), and Γ5(C), respectively. However, the PC intensities decreased with lowering temperature. In the log Jph vs 1/T plot, the dominant level at the high-temperature region was observed and its value was 29.1 meV. This level corresponds to the activation energy for the electronic transition from the edge of the valence band to the shallow acceptor levels caused by these native defects. Consequently, we suggest that the trapping centers due to native defects in BaIn2Se4 layers are responsible for this PC-intensity decrease with decreasing temperature.