Overlapped Graphene Gate β-Ga2O3 MISFETs for Enhancement-Mode Transistor and Nonvolatile Memory Operations

초록

Over the past few years, oxide semiconductors have garnered significant attention as highly promising candidates due to their exceptional physical and electrical properties. As research advances, various materials and methods have been devised to enhance the performance of devices. β-phase gallium oxide (β-Ga2O3) has emerged as a promising ultra-wide bandgap (UWB) semiconductor material for next-generation power electronic and optoelectronic application devices. In this study, we demonstrate a Sn-doped β-Ga2O3-based field-effect transistor (FET), tunable to set as a depletion-mode or an enhancement-mode transistor by modulating the gate bias for versatile device application methods. For the device fabrication, graphene flakes serving as the gate electrode were transferred onto a glass substrate using a PDMS stamping process, followed by the transfer of hexagonal boron nitride (h-BN) as the gate insulator, and β-Ga2O3 flakes as the semiconductor channel layer using the same method. The source and drain electrodes were patterned by photolithography to fabricate the gate-overlapped β-Ga2O3 FET on the bottom graphene electrode. Additionally, Au/E-GaIn electrodes were used as an ohmic contacts to the β-Ga2O3 channel flakes. These results demonstrate that a gate bias could effectively modulate a threshold voltage shift, setting the device into enhancement-mode operation. This gate tunable transition properties of Sn-doped β-Ga2O3 -based MISFETs would be a significant technologies for future power electronics, offering new design flexibility in wide bandgap transistor applications.