First Demonstration of an N-Polar InAlGaN/GaN HEMT

In this letter, we report the first N-polar InAlGaN quaternary back barrier high-electron-mobility transistor (HEMT). The epitaxial device heterostructure was grown by metal organic chemical vapor deposition (MOCVD). Hall measurements of the heterostructure showed a two-dimensional electron gas (2DEG) density of 2.85 x 10 ¹³ cm ^-2 and a mobility of 1048 cm ² s ^-1 V ^-1 . Transfer length method measurements showed a remarkably low sheet resistance of 179 Ω/□ in the source-drain direction. A HEMT with a gate length of 0.6 μm and source-drain spacing of 3.1 μm showed a peak transconductance of 212 mS/mm and a high peak DC drain current of 1.92 A/mm. Small signal measurements of an equivalent HEMT yielded a current-gain cut-off frequency (f _T ) and power-gain cut-off frequency (f _max ) of 18 GHz and 28 GHz, respectively, at peak f _max bias conditions (VGS = -9 V and VDS = 5 V).