Gate leakage current and threshold voltage characteristics of β-Ga2O3 passivated AlGaN/GaN based heterojunction field effect transistor

We report the gate leakage current and threshold voltage characteristics of Al_0.3Ga_0.7N/GaN heterojunction field effect transistor (HFET) with metal-organic chemical vapor deposition (MOCVD) grown β-Ga₂O₃ as a gate dielectric for the first time. In this study, GaN channel HFET and β-Ga₂O₃ passivated metal-oxide-semiconductor-HFET (MOS-HFET) structures were grown in MOCVD using N₂ as carrier gas on a sapphire substrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to characterize the structural properties and surface morphology of the heterostructure. The electrical properties were analyzed using van der Pauw, Hall, and the mercury probe capacitance-voltage (C-V) measurement systems. The 2-dimensional electron gas (2DEG) carrier density for the heterostructure was found to be in the order of ~10¹³ cm^-2. The threshold voltage shifted more towards the negative side for the MOSHFET. The high-low (Hi-Lo) frequency-based C-V method was used to calculate the interface charge density for the oxide-AlGaN interface and was found to be in the order of ~10¹² cm²eV^-1. A remarkable reduction in leakage current from 2.33×10^-2 A/cm² for HFET to 1.03×10^-8 A/cm² for MOSHFET was observed demonstrating the viability of MOCVD-grown Ga₂O₃ as a gate dielectric.