氮極性獨立式氮化鎵基板磷酸蝕刻機制與形貌探討

Abstract

本論文在探討氮極性獨立式氮化鎵磷酸蝕刻的形貌與機制。磷酸被被認是個很方便的酸性溶液在於檢驗氮化鎵基板的品質，但是很少團隊對於磷酸去除氧化物的能力與蝕刻機制的探討。從鎵極性獨立式氮化鎵基板做完XPS的結果來看，氧含量的比例相較於沒做磷酸處理的樣品為30-50%，且從XPS的束縛能往高能階偏移了0.83 eV，可以知道電子濃度在做完磷酸蝕刻後增加了，合理地的就是有氮空缺的形，由此推論氫原子為磷酸蝕刻的主要反應。由拉曼量測結果與其對氫氧化鉀蝕刻的比較後，確立了磷酸的蝕刻機制。藉此去看氮極性氮化鎵基板的磷酸蝕刻形貌。 從結果來看，磷酸不論是在鎵極性面還是氮極性面，都會從表面的缺陷開始攻擊。只要是磷酸蝕刻後的形貌，必會出現鎵極性的穩定面。所以在鎵極性面上會出現V-pits和氮極性面上出現十二面角錐的情況，亦可以使用這個模型來解釋之。

In this work, we study the morphology and etching mechanism on N-face phosphoric acid treatment free-standing GaN. It’s well known that phosphoric acid is good solution to recognize the surface defect on Ga-polar GaN, but it seldom used for removing native oxide on GaN, and discussed the etching mechanism. On XPS measurement, we found that the oxygen content on acid treatment sample was only 30-50% comparing to un-treatment sample, and the binding energy had been shifted 0.83 eV after H3PO4 treatment, it meant that the electron concentration was raised. We infer it be caused by the hydrogen atom. And that was the main reactant on H3PO4 etching. This result verified by Raman measurement and KOH etching mechanism. Finally, we demonstrated that the pyramids appeared on N-face H3PO4 treatment samples, and v-pits formed on Ga-face by etching pits density experiment. All the facets after H3PO4 etching were Ga-polarity.