Enhancing photodetection of WSe₂ phototransistors by reducing charge scattering with hBN passivation

Two-dimensional (2D) semiconductors like tungsten diselenide (WSe 2 ) have significant potential for next-generation phototransistors because of their broad detection range and strong light-matter interaction. However, dielectric disorder at the interface with conventional silicon dioxide (SiO 2 ) substrates hampers the device performance by introducing surface charge traps and oxygen dangling bonds, which degrade carrier transport and increase low-frequency noise (LFN). Here, we show that simply incorporating a hexagonal boron nitride (hBN) passivation layer between WSe 2 and SiO 2 effectively reduces interfacial disorder by creating a clean van der Waals interface through optoelectrical and LFN analysis. The WSe 2 /hBN phototransistors demonstrate a 100-fold decrease in LFN, a 100-fold increase in responsivity, and a 10-fold improvement in specific detectivity compared to WSe 2 devices without an hBN layer. This enhancement in device performance is ascribed to shielding Coulomb scattering and maintaining the intrinsic transport properties of WSe 2 . Our findings underscore the importance of passivating the channel scattering sources of 2D-based phototransistors in enhancing photodetection performance.