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

Abstract

Two-dimensional (2D) semiconductors like tungsten diselenide (WSe2) 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 (SiO2) 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 WSe2 and SiO2 effectively reduces interfacial disorder by creating a clean van der Waals interface through optoelectrical and LFN analysis. The WSe2/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 WSe2 devices without an hBN layer. This enhancement in device performance is ascribed to shielding Coulomb scattering and maintaining the intrinsic transport properties of WSe2. Our findings underscore the importance of passivating the channel scattering sources of 2D-based phototransistors in enhancing photodetection performance.