Polarization-Engineered Quaternary Barrier InAlGaN/AlGaN Heterostructure Field-Effect Transistors Toward Robust High-Frequency Power Performance in AlGaN Channel Electronics

Polarization-engineered Al0.2Ga0.8N channel heterostructure field-effect transistors (HFETs) with quaternary InAlGaN barrier layers have been investigated theoretically and numerically. The polarization-matched (PolM) normally-OFF InAlGaN/Al0.2Ga0.8N HFETs exhibited great breakdown characteristics, in which large breakdown voltage ( ${V}_{B}$ ) and highly efficient modulation of ${V}_{B}$ have been observed by varying the Al composition in the InAlGaN barrier. The electron drift velocity of approximately 1.1 $\times \,\,10^{{7}}$ cm/s, on par with that of the GaN channel HFETs, was achieved and become saturated in the Al0.2Ga0.8N channel of the InAlGaN/Al0.2Ga0.8N PolMHFETs when the ON-state drain bias operated in the current saturation region. Moreover, the electron saturation velocity of the InAlGaN/Al0.2Ga0.8N PolMHFETs showed a little deviation from that of an Al0.2Ga0.8N channel layer at high electric fields which was attributed to the carrier injection from the contacts neglected in the analytical model. As a result, superior RF power performance was obtained for the normally-OFF InAlGaN/Al0.2Ga0.8N PolMHFETs, according to the small- and large-signal simulation results. These findings highlight the advantages and potential of normally-OFF InAlGaN/AlGaN PolMHFETs for applications in high-frequency power electronics enabled by the alternative large ${V}_{B}$ without increasing the device dimension or Al composition in the AlGaN channel and high electron saturation velocity.