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