氮化鎵磊晶層在A軸向與C軸向之奈米壓痕特性分析與陰極螢光檢測

Abstract

本論文主要探討氮化鎵(GaN)磊晶層薄膜在A軸向(11-20)與C軸向(0001)之奈米機械特性，研究中運用奈米壓痕技術，配合反覆覆載破壞方法，探討不同軸向之氮化鎵磊晶層對於負載破壞的抵抗能力。在實驗中使用有機金屬化學氣相磊晶法在藍寶石基材上沈積氮化鎵磊晶薄膜，其後運用奈米壓痕量測系統配合多次循環負載方法，探討氮化鎵磊晶層之奈米機械特性，最後運用陰極螢光技術分析不同軸向氮化鎵磊晶層受到反覆負載破壞後其激發光特性之改變。 由實驗結果可知，在反覆覆載破壞下，不同軸向之氮化鎵磊晶層內部晶格滑移與差排增生的機制與晶格主滑移面有直接關聯性。另一方面，壓痕破壞區之激發光譜呈現降低與偏移之情形，其原因在於磊晶層內部產生差排與原子距離改變。

The purpose of this study is to investigate the nanoindentation properties of Gallium nitride (GaN) epilayers on A-axis (11 0) and C-axis (0001) sapphire substrate. In the experiment procedure, the GaN epilayers was synthesized by metal-organic chemical vapor deposition on C-axis (0001) and A-axis (11 0) sapphire substrate. The nanindentation properties of GaN epilayers has been investigated by using nanoindentation system with repetition pressure force mode. The different nanomechanical (Hardness and elastic-modulus) was determined from cycle nanoindentation, and resulted in a crack due to the formation of incipient slip bands and/or the to-and-fro motion of mobile dislocation. The slip band and dislocation nucleate were indicated that the generation of individual dislocation and residual deformation of the GaN epilayers were shown by cathodoluminescence analysis. The residual indentation impression was measured by means of AFM technique after the nanoindentation beyond the critical depth. In conclusion, the cathodoluminescence study of the indentation impressions show the clear evidence on the observation of the defects transform. This transformation of strain hardening of GaN is occurred under the repetition nanoindenter test. The strain energy is transformed to mobile dislocation and resulted in a pop-in event initially. It is speculated that the repetition pressure-induced impairment was contributed by the multiple pop-in events, and are revealed over the indentation load and penetration depth.