Improve GaN quality with sputter AlN buffer layer on wet-etched and dry-etched PSS

• Main Authors: Li, Jhen-Hong, 李振宏
• Other Authors: Wu, Yew-Chung
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/16153782744911894364

碩士 === 國立交通大學 === 材料科學與工程學系所 === 105 === Light emitting diodes(LEDs) have been replaced incandescent-filament lamp due to their advantages of small size、long life and high efficiency. There are a lot of applications such as car headlight, screen backlight source and street light. The material of LEDs is GaN, but GaN is lack of own’s substrate. As a result, we usually use sapphire as substrate to epitaxy GaN. There are still many problems between sapphire and GaN such as lattice mismatch and thermal expansion coefficient difference, which will make defects and degrade internal quantum efficiency (IQE).So the solution we use is pattern sapphire substrate (PSS) which can make dislocation bending and change the optical path. It will improve IQE and light extraction efficiency(LEE). Our first experiment is using wet-etching to fabricate wet-etched convex-PSS (convex-PSS)and wet-etched concave-PSS(concave-PSS).Then, we sputter AlN on PSS to epitaxy GaN and analysis. In the experiment, we discover GaN quality of convex-PSS is better than concave-PSS and light output power(LOP) of convex-PSS is much better than concave-PSS. It is because the LEE of convex is better. Our second experiment is using dry-etching PSS and modifying AlN buffer layer. The GaN of Top AlN on PSS (TPSS) mainly growth on the cone and difficult to epitaxy smoothly which is difficult to fabricate LED chip. Our expectation of GaN quality is Bottom AlN on PSS(BPSS) is better than AlN on PSS(RPSS),but the truth is in contrast. Because of their almost same LEE, we can determine whose IQE is better by the LOP and we observe the LOP of RPSS is better than BPSS.