Uni-Traveling-Carrier Photodiode Based on MoS2/GaN van der Waals Heterojunction for High-Speed Visible-Light Detection

TL;DR

This paper presents a novel uni-traveling-carrier photodiode using a MoS2/GaN van der Waals heterojunction, enabling high-speed visible-light detection with GHz response and 1% quantum efficiency across the spectrum.

Contribution

It introduces a new heterojunction design for UTC-PDs using 2D MoS2 and GaN, achieving visible-light detection with high-speed performance.

Findings

GHz-range frequency response achieved

Quantum efficiency around 1% across visible spectrum

Successful direct epitaxial growth of MoS2 on GaN

Abstract

Uni-traveling-carrier photodiodes (UTC-PDs), which utilize only electrons as the active carriers, have become indispensable in high-speed optoelectronics due to their unique capabilities, such as high saturation power and broad bandwidth. However, extending the operating wavelengths into the visible region for wider applications is challenging due to the lack of suitable wide-bandgap III-V semiconductor combinations with the necessary band alignment and lattice matching. Here, we show that a UTC-PD based on a van der Waals heterojunction composed of a 2D transition metal dichalcogenide, molybdenum disulfide (MoS2), as a photoabsorption layer and a gallium nitride (GaN) film as a carrier transport layer, offers a solution to this challenge. The fast vertical carrier transport across the heterointerface is enabled by the direct epitaxial growth of a MoS2 layer on a GaN film. Our device demonstrates a frequency response in the several-GHz range with a quantum efficiency on the order of 1% throughout the entire visible spectrum, highlighting the promise for high-speed visible optoelectronics.