藍寶石基板上的圖案尺寸與形狀對氮化鎵磊晶成長的影響

Abstract

本研究是為了改善圖案化藍寶石基板，利用二次蝕刻方式，將原本第一次蝕刻時角錐上的平頂，c-plane，變成尖頂，盡量減少c-plane面積。因為在氮化鎵在磊晶成長時，差排會從氮化鎵跟基板的c-plane產生貫穿差排(Threading dislocations，TDs)，這些缺陷會影響LEDs的光電特性。而經TEM觀察後，相較於一次蝕刻基板，二次蝕刻基板可以更有效減少差排密度，幾乎沒有差排貫穿上去，把差排都局限於角錐的斜面上。在Iv(Intensity)，一次蝕刻的元件比傳統的提升了29.8% ，二次蝕刻的則增強70.25%。Output power方面，在20mA電流驅動下，一次蝕刻的元件比傳統發光二極體提升了13.6%的發光強度，二次蝕刻的更達到了26.5%

This study is to improve the design of patterned sapphire substrate. Using the two step etching , it will minimize c-plane area which is the top of pyramid from one step etching 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 an one step etching substrate, the two step etching substrate can be more effective in reducing the disolcation 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 conventional LED, the sample of one step etching raise 29.8%,and the sample of two step etching increase 70.25%. For output power, in the 20 mA current drive, the sample of one step etching was 13.6% lager than that of the conventional LED , and increased by 26.5% for the sample of two step etching.