極性與非極性氮化物薄膜同質磊晶於氮化鎵基板之成長機制與光電特性研究

Abstract

氮化鎵薄膜是目前最重要的半導體材料研究主題之ㄧ，但是現今的技術是將氮化物異質磊晶在藍寶石基板上，由於氮化鎵和藍寶石有晶格及熱膨脹係數不匹配的問題，因此衍生出異質磊晶產生的大量缺陷以及基板彎曲現象，造成元件性能壽命降低並使得後續製程困難。而利用氮化鎵基板同質磊晶則可解決這些問題，並且具有高導電性、散熱性及劈裂容易等多項優異特性。而本實驗室在先前計畫的支持下，已經能夠穩定成長出氮化鎵基板，期望藉用此次國科會計畫，更進一步提昇台灣在氮化鎵基板上同質磊晶之研究。 本計畫分為三年進行，第一年重點放在氮化鎵基板的製備和氮化鎵薄膜的同質磊晶，預期先利用一年的時間將氮化鎵基板的晶格應力釋放與研磨損害分析，以及完成氮化鎵薄膜同質磊晶機制。第二年將討論同質磊晶氮化鎵薄膜之磊晶品質和特性研究，包括(1)介面與缺陷分析 (2)激子和能階研究 (3)缺陷移動率探討，此外我們將利用不同製程與磊晶方式，嘗試在極性氮化鎵基板上成長出非極性或半極性的氮化鎵薄膜。第三年我們將比較同質磊晶在氮化鎵基板和藍寶石基板之差異，並探討低溫緩衝層對於成長氮化鎵薄膜之影響，最後，我們將在製作出來的氮化鎵基板上，成長極性、半極性和非極性量子井結構，探討其光電特性。

GaN thin film is one of the most important semiconductor material research topics, but the conventional technique of nitride compound semiconductor is hetero-epitaxially grown on sapphire substrates in the present day. Due to the problems of lattice and thermal expansion mismatch between GaN and sapphire, there are huge dislocation densities and bowing of substrate induced through the hetero-epitaxy. These problems will make the performance of devices low lifetime and manufacturing process hard. GaN substrate not only can solve these problems but also has several excellent characteristics, such as high electrical- and thermal- conductivity and clear cleaves face. Our laboratory has achieved to manufacture the GaN substrate in high yields by the support of previous project. We expect further elevate the homo-epitaxial study on GaN substrate in Taiwan through this National Science Council project. This project is divided into three years. The first year, we will focus on the GaN substrate preparation and GaN thin film homo-epitaxial on GaN substrate. We look forward to a year's time will realize the analysis of lattice stress release and polish damage of GaN substrate. Moreover, the mechanism of GaN thin film homo-epitaxial on GaN substrate will also be accomplished. The second year, we will discuss the crystal quality and characteristics of GaN film, which is produced on GaN substrate by homo-epitaxial technique. It includes (1) the defects and interface, (2) the exciton and energy level, and (3) the defect mobility of homo-epitaxial GaN thin film on GaN substrate. And the semi- or non-polar GaN thin films will grow on the c-plane polar GaN substrate by difference manufacturing processes and epitaxial techniques. The last year, we will compare the differences of the GaN thin film grown on GaN and sapphire substrate. Additionally, the influence of the low temperature buffer layer on GaN substrate will also be discussed. Finally, we will study the optoelectrical characteristics of quantum wells including polar, semi- and non-polar grown on GaN substrates.