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

A low-temperature fabrication of Al_xGa_1-xN/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^-6Q-cm² 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_0.23Ga_0.77N/GaN interface-trap density on the order of 10¹¹ cm^-2eV^-1). The demonstrated approach is thus a promising alternative toward the gold-free GaN-on-Si integration.