Wafer-Scale Patterning Synthesis of Two-Dimensional WSe₂ Layers by Direct Selenization for Highly Sensitive van der Waals Heterojunction Broadband Photodetectors

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit promising potential in fabricating highly sensitive photodetectors due to their unique electrical and optoelectrical characteristics. However, micron-sized 2D materials produced by conventional chemical vapor deposition (CVD) and mechanical exfoliation methods fail to satisfy the demands for applications in integrated optoelectronics and systems given their poor controllability and repeatability. Here, we propose a simple selenization approach to grow wafer-scale (2 in.) 2D p-WSe₂ layers with high uniformity and customized patterns. Furthermore, a self-driven broadband photodetector with a p-WSe₂/n-Si van der Waals heterojunction has been in situ fabricated with a satisfactory responsivity of 689.8 mA/W and a large specific detectivity of 1.59 × 10¹³ Jones covering from ultraviolet to short-wave infrared. In addition, a remarkable nanosecond response speed has been recorded under 0.5% duty cycle of the input light. The proposed selenization approach on the growth of 2D WSe₂ layers demonstrates an effective route to fabricate highly sensitive broadband photodetectors used for integrated optoelectronic systems.