Mosaic Structure Evolution in GaN Films with Annealing Time Grown by Metalorganic Chemical Vapour Deposition

• 来源期刊: 中国物理快报（英文版）
• 年，卷（期）: 2006,（5）
• 页码范围: 1257-1260
• 页数: 4页
• 语种: 英文

摘要

We investigate mosaic structure evolution of GaN films annealed for a long time at 800 ℃ grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show that residual stress in GaN films is relaxed by generating edge-type threading dislocations (TDs) instead of screw-type TDs. Compared to as-grown GaN films, the annealed ones have larger mean twist angles corresponding to higher density of edge-type TDs but smaller mean tilt angles corresponding to lower density of screw-type TDs films.Due to the increased edge-type TD density, the lateral coherence lengths of the annealed GaN films also decrease.The results obtained from chemical etching experiment and grazing-incidence x-ray diffraction (GIXRD) also support the proposed structure evolution.