UV to NIR tunable photodetector using Bi₂Te₂Se/n-GaN heterojunction

This study reports Bi₂Te₂Se/n-GaN topological insulator / semiconductor heterojunction fabrication where, Bi₂Te₂Se was thermally evaporated over n-type GaN substrates. X-ray diffraction confirms the poly-crystalline Bi₂Te₂Se film and Hall measurement confirmed it to be n-type. Optical study of the film was performed by Raman analysis and ultrafast transient absorption spectroscopy. Bi₂Te₂Se/n-GaN heterojunction showed good p-n heterojunction diode characteristics with excellent broadband photodetection capabilities. The devices showed photoresponse ranging from near-ultraviolet (UV) to near-infrared (NIR) regions in both the quadrants. Bi₂Te₂Se/n-GaN heterojunction showed excellent responsivity and detectivity at the NIR range (700 nm) which corresponds to the absorption due to Bi₂Te₂Se TI film. The Capacitance-Voltage (C − V), Capacitance-frequency (C − f) and conductance/radial frequency-radial frequency (G_p/ω-ω) plots were studied for the interface traps across the junction to quantify the traps and to find the carrier trap time which is well supported by ultrafast dynamics. The study gives an important perspective for the next-generation topological insulator-GaN based heterojunction optoelectronics devices.