Investigating the Electrical Transport and Photoresponse Properties of WSe2 and a Thermally Engineered SrTiO3-Based Heterojunction

The engineering of functional interfaces plays an essential role in improving the electronic, spintronic, memory, and optoelectronic performances of semiconductor devices. In the present work, such an engineered interface is fabricated using the reduced SrTiO3 (r-STO) in combination with a sputter-deposited WSe2 thin film having Cu electrodes. The current–voltage characteristics of the heterojunctions exhibit a very strong temperature dependence. Interestingly, the I–V characteristics of the device show a remarkably high rectification ratio on the order of ∼105 at low temperatures. A comprehensive investigation of the electrical transport properties was carried out. The analysis revealed that the trap centers present in r-STO along with the grain-induced defect states in the WSe2 thin film lead to the space-charge-limited-conduction-supported mechanism, which explains the higher voltage dependence of the current in the device. The vacant states produced in the bulk are further probed with the help of frequency- and temperature-dependent capacitance–voltage (C–V) characteristics of the device. The C–V characteristics confirm the electronically active interface states and trap centers present in the WSe2/r-STO heterojunction. Along with that, the photoresponse properties of the device show a maximum responsivity of 64.5 A W–1 when illuminated with a wavelength of 1100 nm, with an incident power of 6.47 μW at 10 K.