Normally-off quasi-vertical GaN FinFET on SiC substrate with record small-signal current gain of f(t)=10.2 GHz

Among the vertical GaN transistors, the FinFET is an unipolar device which therefore neither needs p-type doping nor regrowth processes [1]. Large area devices with currents of several amperes and high breakdown voltages beyond 1 kV were presented [2], [3]. So far, the FinFET has been investigated as high-power device and only little interest has been given to his potential as high-frequency transistor [4], [5]. Although normally-off FinFETs were realized on expensive bulk GaN substrates, the sole normally-off FinFET on foreign substrate relied on an introduction of p-GaN, thereby relinquishing the unipolar nature of the FinFET and suffering from the low mobility in the p-channel [6]. In this work, we demonstrate the first normally-off quasi-vertical FinFET on SiC substrate with an analysis of its small-signal performance.