| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 103 === 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.
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