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-MoSe2 thin films with wafer-level uniformity. The reduction of MoO3 was found indispensable for the successful synthesis of MoSe2 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/MoSe2 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 2×1013 Jones for 2D MoSe2/MoS2 PDs. Our findings revealed a pathway for the development of high-performance PDs based on 2D MoSe2 that are inexpensive, large area, and suitable for mass production and contribute to a deep understanding of the photoconductivity mechanisms in atomically thin MoSe2. We anticipate that these results are generalizable to other layer semiconductors as well.
Highlights
Nanomaterials are gaining intense interest in photodetection due to their large surface-to-volume ratios and low dimensions, which can yield higher light sensitivity than their bulk counterparts
We reported a method involving atomic layer deposition and a chemical vapor deposition chamber to produce few-layer 2H-MoSe2 thin films with wafer-level uniformity
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/MoSe2 interface, the band tail state contribution, and the photogating effect
Summary
Nanomaterials are gaining intense interest in photodetection due to their large surface-to-volume ratios and low dimensions, which can yield higher light sensitivity than their bulk counterparts. By employing quantum dots (QDs) [2] and one-dimensional (1D) semiconducting nanostructures of ZrS2, CdS, and ZnO as sensitizers [3,4,5], high-performance photodetectors (PDs) have been demonstrated. Benefiting from the quantum confinement effects in the out-of-plane direction, two-dimensional (2D) materials are highly promising for high-performance optoelectronic devices, which are compatible with current thin-film microfabrication techniques appropriately. The extremely high electrical mobility (up to 200,000 cm2/v/s for both electrons and holes) [6] and vanishing effective mass render graphene a promising candidate for high-speed photodetection, the responsivity of graphene-based PDs is far from satisfactory (~10−3 A/W) mainly due to its short photocarrier lifetime [7], low absorption ratio of incident light (~2%) [8, 9], and external quantum efficiency (EQE; 0.1–0.2%) [10].
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