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 <tex-math notation="LaTeX">2.85× 10^13 </tex-math> cm <tex-math notation="LaTeX">^-2 </tex-math> and a mobility of 1048 cm <tex-math notation="LaTeX">^2\,\,s^-1\,\,V^-1 </tex-math> . Transfer length method measurements showed a remarkably low sheet resistance of <tex-math notation="LaTeX">179~Ω / </tex-math> in the source-drain direction. A HEMT with a gate length of <tex-math notation="LaTeX">0.6~μ m </tex-math> and source-drain spacing of <tex-math notation="LaTeX">3.1~μ m </tex-math> 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 ( <tex-math notation="LaTeX">fT) </tex-math> and power-gain cut-off frequency ( <tex-math notation="LaTeX">fₘₐₓ) </tex-math> of 18 GHz and 28 GHz, respectively, at peak <tex-math notation="LaTeX">fₘₐₓ </tex-math> bias conditions (VGS = −9 V and VDS = 5 V).