Synthesis of few‐layer 2H‐MoSe ₂ thin films with wafer‐level homogeneity for high‐performance photodetector

Abstract

Abstract The unique structural and physical properties of two‐dimensional (2D) atomic layer semiconductors render them promising candidates for electronic or optoelectronic devices. However, the lack of efficient and stable approaches to synthesize large‐area thin films with excellent uniformity hinders their realistic applications. In this work, we reported a method involving atomic layer deposition and a chemical vapor deposition chamber to produce few‐layer 2H‐MoSe 2 thin films with wafer‐level uniformity. The reduction of MoO 3 was found indispensable for the successful synthesis of MoSe 2 films due to the low vaporization temperature. Moreover, a metal‐semiconductor‐metal photodetector (PD) was fabricated and investigated systematically. We extracted an ultrahigh photoresponsivity approaching 101 A/W with concomitantly high external quantum efficiency up to 19,668% due to the produced gain arising from the holes trapped at the metal/MoSe 2 interface, the band tail state contribution, and the photogating effect. A fast response time of 22 ms was observed and attributed to effective nonequilibrium carrier recombination. Additionally, the ultrahigh photoresponsivity and low dark current that originated from Schottky barrier resulted in a record‐high specific detectivity of up to 2×10 13 Jones for 2D MoSe 2 /MoS 2 PDs. Our findings revealed a pathway for the development of high‐performance PDs based on 2D MoSe 2 that are inexpensive, large area, and suitable for mass production and contribute to a deep understanding of the photoconductivity mechanisms in atomically thin MoSe 2 . We anticipate that these results are generalizable to other layer semiconductors as well.