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\times 10^{{13}} cm ^{-{2}} and a mobility of 1048 cm ^{{2}}\,\,\text{s}^{-{1}}\,\,\text{V}^{-{1}} . Transfer length method measurements showed a remarkably low sheet resistance of 179~\Omega /\Box in the source-drain direction. A HEMT with a gate length of 0.6~\mu \text{m} and source-drain spacing of 3.1~\mu \text{m} 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 ( \text{f}_{\text {T}}{)} and power-gain cut-off frequency ( \text{f}_{\text {max}}{)} of 18 GHz and 28 GHz, respectively, at peak \text{f}_{\text {max}} bias conditions (VGS = −9 V and VDS = 5 V).