氮極性面氮化鎵基板之磷酸蝕刻活化能與表面形貌特性研究

Abstract

本論文主要是關於磷酸對氮化鎵基板的蝕刻研究，在氮極性面處可藉由SEM觀察出許多不同特性的十二角錐狀結構。磷酸對兩種不同溫度所形成的氮化鎵磊晶層有著不同的蝕刻速率、不同的活化能及在蝕刻後也有不同的形貌，較低溫(950℃)所成長的氮化鎵被磷酸蝕刻的反應活化能大小為0.33eV，較高溫(1050℃)則為0.51eV。活化能大小會有此差距主要與晶體的缺陷密度有關。另外磷酸幾乎不與鎵極性面反應，推測主要是磷酸根受到鎵極性面氮原子的三根空懸鍵所產生的排斥力影響。此外，不同蝕刻參數包括蝕刻溫度、蝕刻時間皆會影響氮極性面上的金字塔結構密度、大小與角度，本論文將對此做詳細的論述。

This study is about Phosphoric Acid etching on GaN substrate. We can find the nitrogen surface of GaN showed many different characteristics of dodecagonal pyramids which were measured by SEM. When two different kinds of GaN substrate grown at different temperature etched in a H3PO4 solution, results showed different etching rate, different activation energy and different surface morphology. For the lower temperature(950℃) sample, the activation energy is determined to be 0.33 eV and the higher temperature(1050℃) is 0.51eV .The difference in the activation energy is in connection with dislocation density of crystal. For Phosphoric Acid, there were no etching of Ga-polar crystals occurred, and the inertness of Ga-polar GaN is considered to the repulsion between PO43- and three occupied dangling bonds of nitrogen. Moreover, the different etching parameter(etching temperature, etching time) have an influence on the characteristics(density、size、angle) of the pyramids structure. This paper will discuss these in detail.