Semimetal-Monolayer Transition Metal Dichalcogenides Photodetectors for Wafer-Scale Ultraviolet Photonics

TL;DR

This paper demonstrates wafer-scale, high-responsivity UV photodetectors using monolayer MoS$_2$ with semimetal contacts, achieving high efficiency and fast response suitable for integrated photonic circuits.

Contribution

It introduces a novel semimetal-MoS$_2$ device with ohmic contacts, grown via CVD at wafer scale, showing superior optoelectronic performance over traditional metal-contact devices.

Findings

High photoresponsivity of 300 A/W at 77 K in UV

External quantum efficiency ~ 1000 or 10^5%

Rise time of 0.1 ms at 77 K, enabling ~10 kHz operation

Abstract

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS$_2$, are promising candidates for nanoscale photonics because of strong-light matter interactions. However, Fermi level pinning due to metal-induced gap (MIGS) states at the metals-monolayer MoS$_2$ interface limits the application of optoelectronic devices based on conventional metals because of the high contact resistance of the Schottky contacts. On the other hand, a semimetal-TMD-semimetal device can overcome this limitation, where the MIGS are sufficiently suppressed and can result in ohmic contacts. Here we demonstrate the optoelectronic performance of a bismuth-monolayer (1L) MoS$_2$-bismuth device with ohmic electrical contacts and extraordinary optoelectronic properties. To address the wafer-scale production, we grew full coverage 1L MoS$_2$ by using chemical vapor deposition method. We measured high photoresponsivity of 300 A/W in the UV regime at 77 K, which translates into an external quantum efficiency (EQE) ~ 1000 or $10^5$%. We found that the 90% rise time of our devices at 77 K is 0.1 ms, which suggests that the current devices can operate at the speed of ~ 10 kHz. The combination of large-array device fabrication, high sensitivity, and high-speed response offers great potential for applications in photonics that includes integrated optoelectronic circuits.