利用多道次奈米壓痕與陰極螢光量測法對A軸氮化鎵磊晶薄膜機械特性之研究

Abstract

本論文主要研究A軸（1120）氮化鎵磊晶結構之奈米機械性質與相對應陰極螢光性質分析，實驗中，首先使用有機金屬化學氣相磊晶系統，在藍寶石基板上生長高品質氮化鎵磊晶層，使用奈米壓痕量測系統分析機械特性，並運用兩種不同的負載破壞方法探討氮化鎵磊晶層的彈塑性變形行為以及奈米機械性質之變化，配合原子力顯微鏡探討表面形貌變化，最後透過陰極螢光光譜分析塑性區之破壞機制。 由奈米壓痕研究結果可知，藉由不同的壓痕模式產生相異的晶格滑動與差排形成機制，可得到相對應變化之材料的彈塑性變形行為；另一方面，由陰極螢光分析結果顯示，壓痕測試後激發光譜產生強度降低與波峰偏移。此激發光譜的改變在於氮化鎵內部產生大量差排以及原子間距改變所引起。

The purpose of this study is to investigate the effect of nanomechanical properties and relative cathodoluminescence characteristics on A-plane gallium nitride (GaN) epilayers. In the experiment procedure, the high quality GaN epilayers was synthesized by metal-organic chemical vapor deposition (MOCVD) on prismatic A-planes (1120) of sapphire substrate. Two different loading modes were utilized to observe plastic deformation behavior and the nanomechanical properties of GaN epilayers in nanoindentation process. After that, the surface morphologies and failure mechanism of indentation-induced deformed area were analyzed by using Atomic Force Microscopy (AFM) and cathodoluminescence system, respectively. The varied elastoplastic deformation behaviors were obtained by using different loading modes which cause different lattice sliding and dislocation nucleation mechanisms in GaN epilayers. Besides, the degradation of peak intensity and shift of peak wavelength were observed from cathodoluminescence analyses. These variations were due to the generation of large dislocations and changed lattice constant through loading process.