Triple Modulation of MoS<sub>2</sub>/β-Ga<sub>2</sub>O<sub>3</sub> van der Waals Heterojunction on the Response Performance of β-Ga<sub>2</sub>O<sub>3</sub> Deep Ultraviolet Photodetector
Jie Su, Xinhao Chen, Liang Shi, Ben Niu, Jingjing Chang, Jincheng Zhang, Yue Hao
Abstract
A thorough comprehension of the influence mechanisms associated with van der Waals heterojunctions (vdWHs) is crucial for the advancement of high-performance β-Ga 2 O 3 deep-UV photodetectors (DUV PDs). Here, through a multiscale simulation and experiment approach, triple mechanisms (including band alignment, electrode/β-Ga 2 O 3 interface modulation, and grain boundary (GB) passivation) of MoS 2 /β-Ga 2 O 3 vdWHs on the response performance of β-Ga 2 O 3 DUV PD were revealed. We find that the effects of the three mechanisms of MoS 2 /β-Ga 2 O 3 vdWHs with type-I band alignments on the response parameters of β-Ga 2 O 3 DUV PD are inconsistent. Because MoS 2 /β-Ga 2 O 3 vdWH reduces the Schottky barrier of the electrode/β-Ga 2 O 3 interface while increasing the carrier concentration at the β-Ga 2 O 3 GBs. Meanwhile, the type-I band alignment of MoS 2 /β-Ga 2 O 3 vdWH optimizes the external quantum efficiency and response speed. However, the straightforward synergy of these three mechanisms is still difficult to improve all response parameters of β-Ga 2 O 3 DUV PDs, as the MoS 2 /β-Ga 2 O 3 vdWHs do not mitigate the dark current. Notably, the hypothetical type-II band alignment of 2D/β-Ga 2 O 3 vdWH is effective in reducing carrier recombination and dark current. Consequently, simultaneously introducing type-I and type-II band alignments of vdWHs and combining them with the triple modulation mechanisms can optimize all of the response characteristics at the same time. The responsivity and response time improve almost one and 2 orders of magnitude, respectively. Our works offer in-depth insights into the triple modulation mechanism of 2D/β-Ga 2 O 3 vdWH on the β-Ga 2 O 3 DUV PD and provide a guideline to design high-performance β-Ga 2 O 3 DUV PD.