Ultrathin Gallium Oxide as Both Surface Passivation Layer with Conductive Filament Contacts and Alternative Gate Dielectric for 2D MOSFETs

Abstract

2D semiconductor devices undergo significant degradation upon exposure to ambient molecules and contaminants, necessitating effective passivation techniques for protecting both the contact and channel. In this study, ultrathin amorphous gallium oxide (GaO_X) layers are squeeze-printed from liquid gallium and integrated with 2D tungsten disulfide (WS₂) channels, as both surface passivation layers with conductive filament (CF) contacts and alternative gate dielectrics, for WS₂/GaO_X field-effect transistors. The ultrathin GaO_X bilayer gate dielectric exhibits a high critical electric field (≈7.9 MV cm⁻¹) and moderate dielectric constant (3.1). Electrical contacts to the GaO_X-passivated channel are established through irreversible electroforming of the CFs within the ultrathin GaO_X bilayers at the contact region; these bilayers also serve as dielectric passivation layers in the gate and channel regions. The devices display excellent electrical characteristics, including good current saturation, low subthreshold swing (66.6–70.0 mV dec⁻¹), and ultralow hysteresis (0.10–0.12 V), and do not deteriorate after extended storage under ambient conditions. Moreover, this integration of ultrathin GaO_X with WS₂ enables reconfigurable dual-input logic operations (OR, AND) using the top and back gates as inputs. This study underscores the potential of ultrathin and printable GaO_X layers as critical components for alternative dielectric and passivation applications in 2D nanoelectronics.