| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系所 === 98 === This study is to improve the design of patterned sapphire substrate. Using the wet-etching technique , it will minimize c-plane area which is the top of pyramid and the shape of pyramid is variable spires from the flattened. In the GaN epitaxial growth, threading dislocations will generate from the interface between the GaN and c-plane, These defects will affect the device performance. Observed by TEM, compared to a flat-top patterned sapphire substrate, the pyramid patterned sapphire substrate can be more effective in reducing the dislocation density. No dislocation can penetrate the LED structure and most of dislocations are confined to the slope on the pyramid. In Iv (Intensity), compared with flat-top LED, the sample of pyramid LED raise 54%. And the flat-top LED with modification of top is better than pyramid LED.
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