Study on Metal-Oxide Field Effect Transistors of β-Gallium Oxide with AlGaO Spacer Layer Grown on Sapphire for High-Power Device Applications

Abstract

This study utilized metal–organic chemical vapor deposition technology to grow β-Ga₂O₃ epitaxial layers on sapphire substrates and fabricate lateral β-Ga₂O₃ field-effect transistors (FETs). To enhance the performance of these FETs, a β-Ga₂O₃/(Al_0.33Ga_0.67)₂O₃ structure was incorporated. The resulting FETs demonstrated high on-state current (I_on), low on-state resistance (R_on), and a high on–off ratio of drain current, indicating excellent two-dimensional electron gas (2DEG) characteristic offered by β-Ga₂O₃/(Al_0.33Ga_0.67)₂O₃ structure. By optimization of the thickness and doping concentration of β-Ga₂O₃, high-performance 2DEG β-Ga₂O₃ FETs were achieved, which satisfied the stringent requirements for power devices. Notably, the heavily doped β-Ga₂O₃/(Al_0.33Ga_0.67)₂O₃ structure led to a significant improvement in performance, with the saturation current (I_D,sat) increasing from 0.16 to 11.4 mA/mm, a remarkable 6925% increase, and the breakdown voltage rising from 331 to 687 V, an increase of 107.25%. The relative performance of the device with and without AlGaO was also simulated. These enhancements were primarily due to the effective reduction of leakage current density and 2DEG formation by the β-Ga₂O₃/(Al_0.33Ga_0.67)₂O₃ layer, which was grown by the importance of precise growth parameters and structural design in advancing the performance of β-Ga₂O₃ FETs, making them highly promising for high-power applications.