Enhancement of fMAX/fT in α-Ga2O3 MOSFET with ultra-wide bandgap MgO and CaO blocking layers

Abstract

This study analyzes the RF and DC characteristics of a novel α-Ga₂O₃ (Gallium oxide) MOSFET (Metal oxide semiconductor field effect transistor) featuring ultra-wide bandgap Magnesium Oxide (MgO) and Calcium Oxide (CaO) back barriers using Atlas TCAD 2D simulations. The main contribution of this work lies in demonstrating the effectiveness of using MgO and CaO as back barriers to significantly enhance electron confinement, improve electron mobility, and boost RF performance (f_T and f_Max) in α-Ga₂O₃ MOSFETs, which addresses key limitations observed in conventional designs. The device incorporates a high-k Hafnium oxide (HfO₂) dielectric layer to minimize gate leakage current. Additionally, the MgO back barrier serves to confine electrons to the Si-doped α-Ga₂O₃ channel, improving electron mobility and enhancing the overall RF performance. The proposed HfO₂/α-Ga₂O₃/MgO/Sapphire MOSFET demonstrates a peak drain-to-source current (I_DS max) of 42 mA/mm, a high transconductance factor (g_m) of 520 mS/mm, and a large output conductance of 5.7 mΩ⁻¹/mm. The device exhibits a significant improvement in RF performance with an f_T of 5.8 GHz and f_Max of 13 GHz compared to conventional α-Ga₂O₃ MOSFETs. Furthermore, the device shows a remarkable I_ON/I_OFF ratio of 9.8×10⁶, an electric field of 3.3 MV/cm, and a transit angular frequency of 22.5 GHz. These results suggest that the HfO₂/α-Ga₂O₃/MgO/Sapphire-based MOSFET is a promising candidate for future high-speed and high-power electronic applications.