Growth of Large-Area WSe2 and Observation of Photogenerated Inversion Layer in DMOS Configuration

Abstract

Here, we report a full-fledged journey toward the material synthesis and characterization of a few-layered/thin WSe₂ using sputtered W-films on SiO₂/Si substrates followed by electrical studies under dark and illumination conditions. A growth temperature of 500 °C and a gas flow rate of 55 sccm are found to be the optimized parameters for the formation of thermodynamically stable WSe₂ with a dominant Raman peak at 265 cm^–1. XRD and HR-TEM measurements clarify the formation of high crystallinity along the c-axis and quasi-crystallinity along the a and b axes, respectively. Lower intensities from Raman measurement and PL peak at 768 nm (with 532 nm excitation wavelength) infers the thin nature of the grown film. This work also retracks the controlled etching by reactive ions to achieve large-area bi/trilayer films to fabricate high-performance devices. An advanced dual MOS (DMOS) structure on the SiO₂/p-Si substrate is fabricated, which shows tremendous performance by means of photocapacitance under illumination condition where photocarriers can survive the higher probe frequencies. Under illumination conditions, the DMOS device demonstrates superior performance, exhibiting a significantly strong electron-inversion region compared to that of HfO₂/SiO₂/p-Si and SiO₂/p-Si MOS devices, even at high frequencies (1–10 MHz). This work thus presents a potential approach for capacitance-based, highly sensitive photodetection within conventional Si technology enabled by integrating WSe₂/W as the active material.