利用氫化物氣相磊晶法在藍寶石基板上直接成長氮化鎵厚膜

Abstract

本論文為了簡化製程及減少外來污染等目的，捨棄一般配合有機金屬氣相磊晶法的前置磊晶膜板的製程，利用水平式自組之氫化物氣相磊晶系統直接在藍寶石基板上成長氮化鎵的厚膜，流程包括氣體淨化、氮化處理、低溫氮化鎵緩衝層成長、高溫氮化鎵厚膜成長等四個階段，且完全在同一個腔體中完成。在低溫緩衝層的部分，發現在低壓高五三比的環境有著較適合緩衝層成長的結果。而經由調整緩衝層參數更可以發現從拉曼光譜量測與蝕刻缺陷密度數據而知道，隨著厚度的增加，厚膜品質將隨之降低，但應力也有逐漸釋放的結果，因此必須以較低溫厚膜配合薄緩衝層故為較理想的參數，經過一連串的假設與嘗試，我們也終於成功製造出1.8吋的無明顯表面缺陷的氮化鎵厚膜，可供之後配合雷射剝離技術以製成獨立式氮化鎵基板。

In this research, we deposit GaN thick films on bare sapphire directly substrate ,without general template made by MOCVD, in a home-made horizontal system of hydride vapor phase epitaxy(HVPE). This alteration will simplify the process, lower the cost, and prevent pollution in the air. Basic process includes cleaning, nitridation, LT-GaN buffer-layer growth, HT-GaN thick-film growth. In the research of buffer-layer, we know that environment of low pressure and high V/III ratio will be beneficial to produce suitable GaN buffer layer. Besides, by analyzing the data of Raman spectrum and EPD, we found thicker buffer layer would lead to worst crystal quality and lower compressive stress. Finally after a series of experiments , we successfully produce 1.8”mirror-like GaN thick film on sapphire to provide the material of free-standing GaN substrate.