Work-function engineering in novel high Al composition Al0.72Ga0.28N/AlN/GaN HEMTs

In this paper, device performance of high Al composition Al
_0.72
Ga
_0.28
N/AlN/GaN HEMTs with ALD Al
₂
O
₃
dielectric is reported. Employing different gate metals, the threshold voltages were shifted by -0.8 V in 0.5-μm-long HEMTs, which indicates an unpinned Fermi level at the ALD Al
₂
O
₃
/ Al
_0.72
Ga
_0.28
N interface. With lower contact resistances, high Al AlGaN HEMTs are well suited for further lateral and vertical scaling to push towards high frequency E/D-mode performance.