Study of high Al fraction in AlGaN barrier HEMT and GaN and InGaN channel HEMT with In0.17Al0.83N barrier

Abstract

This paper investigates to find a method to improve the design parameters such as drain current, transconductance, cut off frequency and most importantly minimum noise figure of the Nitride HEMTs. Firstly, to improve the performance of the Nitride HEMT, the AlGaN barrier with high Al fraction was used. Owing to its higher carrier density at higher Al fraction, AlGaN/GaN HEMT exhibited higher drain current, higher transconductance. It also results in a lower minimum noise figure. But, the increase of Al in barrier leads to a lattice mismatch of barrier layer with GaN channel layer. Thus, In0.17Al0.83N barrier layer which is lattice matched to GaN is used instead of traditionally popular AlGaN. Along with a change of material of the barrier layer, a change of material of the channel layer shows improvement in DC & RF response and most importantly in the minimum noise figure when InGaN replaces GaN. The noise performance has been further improved with the T-shaped gate by reducing the gate resistance. All the theoretical analyses have been supported and verified by the results obtained from simulation carried out using Silvaco TCAD tool.