Structure and Strain Properties of GaN Films Grown on Si (111) Substrates with Al sub(x)Ga sub(1-x) N/Al sub(y)Ga sub(1-y)N Superlattices

• Published in: Chinese physics letters Vol. 32; no. 5; pp. 058103 - 1-058103-4
• Main Authors: Pan, Lei, Ni, Jin-Yu, Yu, Xin-Xin, Dong, Xun, Peng, Da-Qing, Li, Chuan-Hao, Li, Zhong-Hui, Chen, Tang-Sheng
• Format: Journal Article
• Language: English
• Published: 01.05.2015
• Subjects: Aluminum; Compressive properties; Cracks; Crystal structure; Dislocations; Silicon substrates; Superlattices; Thick films
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/32/5/058103

GaN films with an Al sub(x)Ga sub(1-x)N/Al sub(y)Ga sub(1-y)N superlattice (SL) bufer layer are grown on Si(111) substrates by metal-organic chemical vapor deposition (MOCVD). The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the GaN layers are strongly dependent on the diference of the Al composition between Al sub(x)Ga sub(1-x)N barriers and Al sub(y)Ga sub(1-y)N wells in the SLs. With a large Al composition diference, the GaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the GaN layer degrades due to the poor function of the SLs in fltering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained GaN film with an improved crystalline quality is achieved. Therefore, the Al sub(x)Ga sub(1-x)N/Al sub(y)Ga sub(1-y)N SL bufer layer is a promising bufer structure for growing thick GaN films on Si substrates without crack generation.