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

Polarization-engineered Al
_0.2
Ga
_0.8
N channel heterostructure field-effect transistors (HFETs) with quaternary InAlGaN barrier layers have been investigated theoretically and numerically. The polarization-matched (PolM) normally-OFF InAlGaN/Al
_0.2
Ga
_0.8
N 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 Al
_0.2
Ga
_0.8
N channel of the InAlGaN/Al
_0.2
Ga
_0.8
N PolMHFETs when the ON-state drain bias operated in the current saturation region. Moreover, the electron saturation velocity of the InAlGaN/Al
_0.2
Ga
_0.8
N PolMHFETs showed a little deviation from that of an Al
_0.2
Ga
_0.8
N 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/Al
_0.2
Ga
_0.8
N 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.