Analysis of transconductance characteristic of AlGaN/GaN HEMTs with graded AlGaN layer

¹ Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, 100083 Beijing, P.R. China
² Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, 100083 Beijing, P.R. China
³ ISCAS-XJTU Joint Laboratory of Functional Materials and Devices for Informatics, 710049 Xi’an, P.R. China

^a e-mail: xlwang@semi.ac.cn

Received: 8 August 2013
Revised: 9 February 2014
Accepted: 26 March 2014
Published online: 5 June 2014

Abstract

A theoretical study of transconductance characteristics (g_m − V_gs profile) of AlGaN/GaN high electron mobility transistors (HEMTs) with a graded AlGaN layer is given in this paper. The calculations were made using a self-consistent solution of the Schrödinger-Poisson equations and an AlGaN/GaN HEMTs numerical device model. Transconductance characteristics of the devices are discussed while the thickness and Al composition of the graded AlGaN layer are optimized. It is found that graded AlGaN layer structure can tailor device’s g_m − V_gs profile by improving polar optical phonon mobility and interface roughness mobility. Good agreement is obtained between the theoretical calculations and experimental measurements over the full range of applied gate bias.