WSe2/β-Ga2O3 p–n Heterojunction-Based Normally Off Phototransistors for Self-Powered UV-C Detection

A WSe 2 /β-Ga 2 O 3 heterojunction (HJ)-based enhancement-mode (E-mode) phototransistor with self-powered operation was developed for ultraviolet-C (UV-C) photodetector applications, featuring a top-gate p-type WSe 2 (p-WSe 2 ) and an n-type ultrawide-bandgap β-Ga 2 O 3 that serves as both the conductive channel and UV-C absorption layer. To increase the hole concentration in WSe 2 dry-transferred onto β-Ga 2 O 3, the top few layers of WSe 2 were oxidized to tungsten oxide (WO x ) (2 < x < 3) with a high work-function value via UV–ozone treatment. High-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed excellent interface quality with atomic-scale layer uniformity in the HJ of WO x /WSe 2 /β-Ga 2 O 3 . The WSe 2 /β-Ga 2 O 3 p–n HJ diode exhibited a high rectification ratio (∼10 9 ) and an extremely low reverse current (14 fA), allowing the demon…