Modulation of optoelectronic properties of the Bi2Te3 nanowire by controlling the formation of selective surface oxidation

In this study, a native oxide layer was transformed from TeO2 into Bi2O3 on Bi2Te3 by changing the annealing temperature, and the change in the effects of the interface between the oxide layers and Bi2Te3 nanowire (NW) was studied. Caused by the change in the surface oxide layer, the change in the interface between the Bi2Te3 NW and oxide layer depending on the annealing temperature alters the band-alignment and charge states of defects, which significantly modulates the carrier dynamics (optical excitation and recombination processes) at the interface. Because of the trap/de-trap processes at a defect of the Bi2Te3/TeO2 interface, the photoresponse of the Bi2Te3/TeO2 system shows the defect-induced photogating effect, whereas the photoresponse of the Bi2Te3/Bi2O3 system shows a capacitive response without trap/de-trap processes. The systematic analysis of the effects of the surface oxidation and related defects on the photoresponse of TIs gives insight into TI-related photodetector devices and their properties under various conditions. Finally, a simple method for controlling the oxidation of the surface and accompanied interface properties such as the valance band offset (VBO), conduction band offset (CBO), and trap/de-trap processes, which can directly affect the operation of TI-based photodetector devices, is proposed.