Al $x$ Ga1–xN/GaN MISHEMTs With a Common Gold-Free Metal-Stack for Source/Drain/Gate

A low-temperature fabrication of Al
_x
Ga
_1-x
N/GaN MISHEMTs on a 200-mm GaN-on-Si substrate using a common metal stack (Ti/Al/NiV) for concurrent source, drain, and gate formation is demonstrated. An ohmic contact resistance of 0.8 Q-mm and a specific contact resistivity of 6×10
^-6
Q-cm
²
are achieved at an annealing temperature of 500 °C. The fabricated MISHEMTs have excellent electrical characteristics: an I
_ON
/I
_OFF
ratio of nine decades (due to subnanoampere OFF-state leakage current up to a -15 V gate bias), and a subthreshold swing of 80 mV/decade (by virtue of a relatively low Al
_0.23
Ga
_0.77
N/GaN interface-trap density on the order of 10
¹¹
cm
^-2
eV
^-1
). The demonstrated approach is thus a promising alternative toward the gold-free GaN-on-Si integration.