First Demonstration of an N-Polar InAlGaN/GaN HEMT
Robert Hamwey, Nirupam Hatui, Emre Akso, Feng Wu, Christopher Clymore, S. Keller, James S. Speck, Umesh K. Mishra
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.85\times 10^{{13}}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{2}}$ </tex-math></inline-formula> and a mobility of 1048 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\,\,\text{s}^{-{1}}\,\,\text{V}^{-{1}}$ </tex-math></inline-formula> . Transfer length method measurements showed a remarkably low sheet resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$179~\Omega /\Box $ </tex-math></inline-formula> in the source-drain direction. A HEMT with a gate length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.6~\mu \text{m}$ </tex-math></inline-formula> and source-drain spacing of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.1~\mu \text{m}$ </tex-math></inline-formula> 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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{f}_{\text {T}}{)}$ </tex-math></inline-formula> and power-gain cut-off frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{f}_{\text {max}}{)}$ </tex-math></inline-formula> of 18 GHz and 28 GHz, respectively, at peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{f}_{\text {max}}$ </tex-math></inline-formula> bias conditions (VGS = −9 V and VDS = 5 V).