中国物理B ›› 2011, Vol. 20 ›› Issue (9): 97701-097701.doi: 10.1088/1674-1056/20/9/097701

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

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

刘子扬, 张进成, 段焕涛, 薛军帅, 林志宇, 马俊彩, 薛晓咏, 郝跃   

  1. School of Microelectronics, and State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, Xidian University, Xi'an 710071, China
  • 收稿日期:2011-01-19 修回日期:2011-04-25 出版日期:2011-09-15 发布日期:2011-09-15

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

Liu Zi-Yang(刘子扬), Zhang Jin-Cheng(张进成)†, Duan Huan-Tao(段焕涛), Xue Jun-Shuai(薛军帅),Lin Zhi-Yu(林志宇), Ma Jun-Cai(马俊彩), Xue Xiao-Yong(薛晓咏), and Hao Yue(郝跃)   

  1. School of Microelectronics, and State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, Xidian University, Xi'an 710071, China
  • Received:2011-01-19 Revised:2011-04-25 Online:2011-09-15 Published:2011-09-15

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

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

Key words: cap layer, strain relaxation, AlGaN/GaN, transport properties

中图分类号:  (Strain-induced piezoelectric fields)

  • 77.65.Ly
72.10.Fk (Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)) 72.80.Ey (III-V and II-VI semiconductors)