Large area MoSe₂ and MoSe₂/Bi₂Se₃ films on sapphire (0001) for near-infrared photodetection

The fabrication of heterojunction-based photodetectors (PDs) is well known for the enhancement of PDs performances, tunable nature of photoconductivity, and broadband application. Herein, the PDs based on MoSe 2 and MoSe 2 /Bi 2 Se 3 heterojunction on sapphire (0001) substrates were deposited using a r.f. magnetron sputtering system. The high-resolution x-ray diffraction and Raman spectroscopy characterizations disclosed the growth of the 2-H phase of MoSe 2 and the rhombohedral phase of Bi 2 Se 3 thin films on sapphire (0001). The chemical and electronic states of deposited films were studied using x-ray photoelectron spectroscopy and revealed the stoichiometry growth of MoSe 2 . We have fabricated metal-semiconductor–metal type PD devices on MoSe 2 and MoSe 2 /Bi 2 Se 3 heterojunction and the photo-response measurements were performed at external voltages of 0.1–5 V under near-infrared (1064 nm) light illumination. The bare MoSe 2 PD device shows positive photoconductivity behavior whereas MoSe 2 /Bi 2 Se 3 heterojunction PD exhibits negative photoconductivity. It was found that the responsivity of MoSe 2 and MoSe 2 /Bi 2 Se 3 heterojunction PDs is ~ 1.39 A W −1 and ~ 5.7 A W −1 , respectively. The enhancement of photoresponse of MoSe 2 /Bi 2 Se 3 PD nearly four-fold compared to bare MoSe 2 PD shows the importance of heterojunction structures for futuristics optoelectronic applications.