| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 102 === 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.
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