The influence of the InGaN back-barrier on the properties of Al_0.3Ga_0.7N/AlN/GaN/InGaN/GaN structure

¹ Materials Science Center, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P.R. China
² Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P.R. China

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

Received: 20 April 2011
Accepted: 4 May 2011
Published online: 21 July 2011

Abstract

This is a theoretical study of the InGaN back-barrier on the properties of the Al₀₃Ga_0.7N/AlN/GaN/InGaN/GaN HEMT structure by self-consistently solving coupled Schrödinger and Poisson equations. Our calculation shows that by increasing the indium composition, the conduction band of the GaN buffer layer is raised and the confinement of 2DEG is improved. However, the additional quantum well formed by InGaN becomes deeper, inducing and confining more electrons in it. Another conductive channel is formed which may impair the device performance. With the increasing InGaN thickness, the well depth remains the same and the conduction band of GaN buffer layer rises, enhancing the confinement of the 2DEG without inducing more electrons in the well. The 2DEG sheet density decreases slightly with the indium composition and the physical mechanism is discussed. Low indium composition and thick InGaN back-barrier layer are beneficial to mitigate the short-channel effects, especially for high-frequency devices.