Insight into the Effect of h-BN Modification on the Performance of MoS₂ Phototransistors with van der Waals Contacts

To adapt to future applications in traditional silicon-based integrated circuits, most of the research on MoS2 phototransistors is currently conducted on Si/SiO2 substrates. However, the SiO2 surface contains a large number of dangling bonds, defects, and impurities, which serve as charge traps that severely affect the performance of MoS2 phototransistors. In this paper, we fabricated MoS2 and h-BN/MoS2 phototransistors with van der Waals contacts using an all-dry transfer technique. Compared to MoS2 devices, the h-BN/MoS2 devices exhibit a higher on/off ratio, larger carrier mobility, faster response speed, larger photoelectric fitting index (α), and smaller hysteresis, while there is a certain extent reduction in responsivity and external quantum efficiency. These results are attributed to the introduction of the h-BN substrate modification layer, which isolates the influence of dangling bonds, defects, and impurities of the SiO2 substrate surface, significantly reducing hole traps at the interface. At the same time, this also weakens the photogating effect in the devices. This work comprehensively explains the interconnected effect and mechanisms of h-BN modification on various aspects of device performance in MoS2 phototransistors fabricated using the all-dry transfer technique, paving the way for designing van der Waals optoelectronic devices with different functionalities and performance in the future.