Comprehensive Study of Normally-off ScAlN Barrier GaN Transistors on Ultra-wide Bandgap β-Ga2O3: DC and RF Perspectives

Abstract This study presents the DC and RF characteristics of an enhancement-mode p-GaN/ScAlN/GaN High Electron Mobility Transistor (HEMT) on an ultra-wide bandgap (Eg > 4.3 eV) β-Ga2O3 substrate. The Scandium Aluminum Nitride (ScAlN) layer improves two-dimensional electron gas (2DEG) confinement, minimizing carrier scattering and enhancing electron transport. The ScAlN barrier offers greater flexibility in bandgap and polarization engineering compared to conventional AlGaN, enabling better control of device characteristics. The proposed HEMT with LG = 0.8 µm, LGD = 5 µm, and LGS = 1 µm demonstrates a drain current density (IDS) of 2.89 A/mm, an on-resistance of 3.29 Ω·mm, a peak transconductance (gm) of 0.561 S/mm, a transit frequency (fT) of 156 GHz, and a breakdown voltage (VBR) of 534 V. The HEMT with field-plate configuration exhibits an improved VBR of 771 V with a trade-off in cut-off frequency. The high electron mobility in the ScAlN/GaN heterostructure, combined with the superior breakdown characteristics of β-Ga2O3, results in high cut-off frequencies with excellent breakdown performance, which is critical for high-power radio frequency systems.