氮化鎵之奈米機械特性與其陰極螢光分析

Abstract

氮化鎵發光二極體具有元件壽命長、啟動電壓低、低耗電量、高亮度以及發光波長涵蓋整個可見 光等優點，使得氮化鎵發光二極體應用廣泛並成為最具有發展性的化合物半導體。研究中使用有機金 屬化學氣相磊晶法分別在C 軸(0 0 0 1)與A 軸(1 1 2 0)晶面之藍寶石基材上成長氮化鎵磊晶層。 本計畫目的為研究氮化鎵磊晶薄膜物理與光電特性，本研究主要在於探討氮化鎵磊晶結構受到奈 米壓痕系統破壞後，磊晶結構所產生的晶格錯位與疊差對於物理機械特性的影響，其後並使用陰極螢 光系統量測氮化鎵磊晶表面與斷面激發光特性的改變，更進一步分析氮化鎵磊晶結構的相位轉換以及 相對應激發光失效機制。 氮化鎵磊晶層之微結構與表面形態利用穿透式電子顯微鏡與原子力顯微鏡分析，結晶結構藉由X 光繞射頻譜儀分析，對於硬度、彈性模數、摩擦係數等機械特性，利用奈米壓痕與奈米刮痕系統配合 接觸式剛性量測以及力量控制方法分析。

Gallium nitride (GaN) have been used for the light emitting diodes(LED) and laser devices, because of its direct gap, wide band gap, and high illumination. In this study, the GaN epilayers will be synthesized by metal-organic chemical vapor deposition (MOCVD) on basal C (0 0 0 1) and prismatic A (1 1 2 0) planes of sapphire crystal. The purpose of this study is to determine the the effect of lattice mismatch and the dislocation activity on the physical properties of GaN epilayers after deformation by nanoindentation test. The failure mechanism of GaN will be investigated by the cathodoluminescence analysis from the observation of the deformed surface. The mircostructure and surface morphology are analyzed using cross-sectional transmission electron microscopy (XTEM) and atomic force microscopy (AFM). Crystalline structure of the deposited films is investigated by using X-ray diffraction (XRD). Hardness, elastic modulus, and friction coefficient of the deposited films are measued by using nanoindenter and the nanoscratch test. Depth-sensed nanoindentation testing coupled with continuous stiffness measurement technique (CSM) is employed to determine the nanomechanical properties of GaN epilayers. In order to understand the nanoindentation mechanism and improve subsequently cathodoluminescence emission quality for GaN epilayers, the relation of lattice mismatch and disformation by nanoindentation test will be investigated in this project.