Performance enhancement of asymmetric gate graded-AlGaN/GaN HEMT on β-Ga2O3 substrate for RF applications

Abstract

This study examines asymmetric gate AlGaN/GaN HEMTs on $\beta$-Ga${}_2$O${}_3$ substrate with different gate positioning and graded Al composition (0$\text{\%}$–30$\text{\%}$) in AlGaN barrier. The graded design improves electron mobility by reducing Al concentration, minimizing scattering, and enabling E-mode operation. It also flattens transconductance peaks and mitigates short-channel effects. Although 2DEG density decreases slightly, it is restored by $n^{+}$GaN-doped contacts. The $\beta$-Ga${}_2$O${}_3$ substrate reduces lattice mismatch with GaN thereby boosting drain current and cut-off frequency. A peak transconductance of 640 mS/mm, cutoff frequency of 55 GHz, and maximum frequency of oscillation of 125 GHz have been obtained. It has been found that optimized gate placement (0.25 $\mu$m from source) yields a gain-frequency product of 2352.24 GHz and gain-bandwidth product of 386.82 GHz for 5 $\mu$m channel and 0.2 $\mu$m gate length. These results highlight superior DC and RF performance of the proposed device making it a promising candidate for high-frequency applications.