本實驗主要是為探討濕式蝕刻於氮化鎵磊晶層上之運用，因目前為提升光萃取效率而對氮化鎵磊晶層進行表面粗化，以及化學濕式剝離法等皆會於氮化鎵磊晶層上進行濕式蝕刻，有鑑於此方面研究並未有完整探討極整理，故於研究我們運用不同的蝕刻溶液以進行濕式蝕刻來蝕刻在藍寶石(sapphire)基板上的氮化鎵無摻雜層(un-doped GaN)，並探討不同的蝕刻溶液、溫度及時間下對蝕刻深度和表面形貌的影響。 本實驗所運用的氮化鎵磊晶層是以有機金屬化學氣相沉積法(Metal-organic Chemical Vapor Deposition, MOCVD)進行磊晶成長於藍寶石基板上，因本實驗選用之藍寶石基板為c軸方向，因此氮化鎵磊晶的方向為沿著c軸成長，而因不同蝕刻溶液對不同極性面有不同的蝕刻現象，因此本論文將對濕式蝕刻之機制做深入的探討。 研究上發現氮化鎵磊晶層上進行濕式蝕刻會與其蝕刻能障係數相關，而當蝕刻能障係數大於m-plane時則無法被蝕刻出也無法觀察到，蝕刻上不論運用酸或鹼蝕刻液其蝕刻出平面主要以(10(11) ¯)為主。 This study use the different etchants to do wet-etching process on the un-doped GaN epi-layer on sapphire substrate. We investigate in detail about the depth and morphology by different etching conditions. In this experiment, metal-organic chemical vapor deposition (MOCVD) was used to regrow un-doped GaN on sapphire substrate. And then, c-plane GaN epi-layer was used to the basic substrate for etching study. The different polarities face have respective phenomenon in etching process. Therefore, this study will discuss the different etching behaviors of GaN epi-layer. Finally, we found that molten KOH will etch the plane of (101 ¯2) and (101 ¯1 ¯ ) at 180°C. The etching will get more energy to do shrinkage, when we enhance the temperature to 260°C, and then the plane will change to (11 ¯00) and (101 ¯1 ¯ ). The H3PO4 will etch the plane of (11 ¯00) and (101 ¯1 ¯ ) at 180°C and 260°C. And then, the H3PO4+H2SO4 will etch the plane (101 ¯1 ¯ ) only at 180°C and 260°C.
