title: Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method.
abstract: Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.
authors.affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P, O, Box 912, Beijing 100083, People's Republic of China. liujianming@semi.ac.cn.
authors.forename: Jianming
authors.initials: J
authors.lastname: Liu
authors.forename: Xianlin
authors.initials: X
authors.lastname: Liu
authors.forename: Chengming
authors.initials: C
authors.lastname: Li
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Wei
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
authors.forename: Chunmei
authors.initials: C
authors.lastname: Jiao
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Li
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Xu
authors.forename: Huaping
authors.initials: H
authors.lastname: Song
authors.forename: Shaoyan
authors.initials: S
authors.lastname: Yang
authors.forename: Qinsen
authors.initials: Q
authors.lastname: Zhu
authors.forename: Zhanguo
authors.initials: Z
authors.lastname: Wang
authors.forename: Anli
authors.initials: A
authors.lastname: Yang
authors.forename: Tieying
authors.initials: T
authors.lastname: Yang
authors.forename: Huanhua
authors.initials: H
authors.lastname: Wang