Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures

作     者：刘子扬 张进成 段焕涛 薛军帅 林志宇 马俊彩 薛晓咏 郝跃 

作者机构：School of Microelectronicsand State Key Discipline Laboratory of Wide Band Gap Semiconductor TechnologyXidian University 

出 版 物：《Chinese Physics B》 (中国物理B（英文版）)

年 卷 期：2011年第20卷第9期

页      面：425-429页

核心收录：

学科分类：080903[工学-微电子学与固体电子学] 0809[工学-电子科学与技术（可授工学、理学学位）] 07[理学] 070205[理学-凝聚态物理] 08[工学] 080501[工学-材料物理与化学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：Project supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No.2008ZX01002-002) the Major Program and the Key Program of National Natural Science Foundation of China (Grant Nos.60890191 and 60736033) 

主　　题：cap layer strain relaxation A1GaN/GaN transport properties 

摘      要：The strain relaxation of an A1GaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of A1GaN/GaN heterostructures. Compared with the slight strain relaxation found in A1GaN barrier layer without cap layer, it is found that a thin cap layer can induce considerable changes of strain state in the A1GaN barrier layer. The degree of relaxation of the A1GaN layer significantly influences the transport properties of the two-dimensional electron gas （2DEG） in A1GaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the A1GaN barrier, which is believed to be the main cause of the deterioration of crystalline quality and morphology on the A1GaN/GaN interface. On the other hand, both GaN and A1N cap layers lead to a decrease in 2DEC density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between CaN and A1GaN, while the reduction of the piezoelectric effect in the A1GaN layer results in the decrease of 2DEC density in the case of A1N cap layer.