氫氣蝕刻氮化鎵及其後續成長之研究

Abstract

本論文研究探討了在不同氣壓下氫氣蝕刻氮化鎵的作用，並應用於氮化鎵的磊晶。我們選擇以氣壓100 torr作為後續成長實驗中的氫氣蝕刻條件，在此蝕刻條件下氮化鎵表面會形成高深寬比且密度高達6.2×109cm-2的小孔洞。接著在氮化鎵成長實驗中我們探討了溫度與氣壓變化對氮化鎵形貌產生的影響，並在氫氣蝕刻後的樣板上進行磊晶。經長時間氫氣蝕刻後的氮化鎵樣板由於表面極為粗糙所以無法成長表面平坦的厚膜。為了使氮化鎵樣板表面平坦，我們設計實驗將二氧化矽填入孔洞，並以拋光液研磨樣板表面；我們能在這種氮化鎵樣板上成長出高品質的氮化鎵厚膜，並且經由雷射剝離技術能獲得幾乎沒有翹曲度的獨立式氮化鎵厚膜。

In this work, we study the effects of hydrogen etching on GaN surfaces at different pressures and the overgrowths of GaN. After hydrogen etching at the pressure of 100 torr, the holes with high aspect ratios appear on GaN surface, and the density of the holes is about 6.2×109cm-2; we perform hydrogen etching under this condition in the following GaN growth experiments. In growing GaN, we discuss the temperatures and pressures effects on GaN profiles and also grow epitaxy layers on hydrogen-etched templates. On long-time-etched templates, they are too rough to obtain flat surface GaN thick films. To flatten the surfaces of templates, we fill holes with silicon oxide and polish the surfaces with slurries; by using this kind of template, we can grow a high quality GaN thick film and, after laser lift-off process, get a free-standing GaN thick film, which is almost without bowing.