Triple Modulation of MoS2/β-Ga2O3 van der Waals Heterojunction on the Response Performance of β-Ga2O3 Deep Ultraviolet Photodetector

A thorough comprehension of the influence mechanisms associated with van der Waals heterojunctions (vdWHs) is crucial for the advancement of high-performance beta-Ga2O3 deep-UV photodetectors (DUV PDs). Here, through a multiscale simulation and experiment approach, triple mechanisms (including band alignment, electrode/beta-Ga2O3 interface modulation, and grain boundary (GB) passivation) of MoS2/beta-Ga2O3 vdWHs on the response performance of beta-Ga2O3 DUV PD were revealed. We find that the effects of the three mechanisms of MoS2/beta-Ga2O3 vdWHs with type-I band alignments on the response parameters of beta-Ga2O3 DUV PD are inconsistent. Because MoS2/beta-Ga2O3 vdWH reduces the Schottky barrier of the electrode/beta-Ga2O3 interface while increasing the carrier concentration at the beta-Ga2O3 GBs. Meanwhile, the type-I band alignment of MoS2/beta-Ga2O3 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 beta-Ga2O3 DUV PDs, as the MoS2/beta-Ga2O3 vdWHs do not mitigate the dark current. Notably, the hypothetical type-II band alignment of 2D/beta-Ga2O3 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/beta-Ga2O3 vdWH on the beta-Ga2O3 DUV PD and provide a guideline to design high-performance beta-Ga2O3 DUV PD.