利用改善載子分佈行為降低氮化銦鎵發光二極體 效率下降特性之研究

Abstract

於本論文中，我們改良傳統氮化銦鎵發光二極體主動層之磊晶結構，以改善載子在主動區中分佈情況來提升氮化銦鎵發光二極體於高電流之發光效率，改善氮化銦鎵發光二極體效率隨外加電流提高而下降之問題。 第一部分，我們在位能井鄰近的位能障，摻入矽和鎂使得位能障變成n型和p型半導體，期望載子能在主動區中適當分佈，使電子和電洞均勻分布於主動層，藉提升主動層載子發光複合效率。我們先以模擬軟體Advanced Physical Models of Semiconductor Devices (APSYS)做理論計算，並得到較好之結果，降低發光效率於高電流注入下將產生效率下降之情況。 第二部分，我們對第一部分模擬結果作更進一步之模擬分析，於模擬結構上我們將第一部分的結構進行選擇性地替放置到不同的位能井，於模擬結果顯示將結構放置在第五層位能井，能增加發光二極體發光複合效率，並且較放到其他位能井發光二極體之效果更佳，也減緩發光效率於高電流注入下產生效率下降之情況。 第三部分，我們將靠近p型半導體的位能井變薄，使得載子容易達到飽和，往下一個位能井傳輸，期望載子在主動區中可以均勻分佈，以提升發光二極體的發光效率，模擬結果顯示，變薄的位能井越多整體的效率會降低，但如果我們以選擇性的方式，將部分位能井變薄，即有改善大電流下發光二極體效率不佳的情況。我們先以模擬軟體Advanced Physical Models of Semiconductor Devices (APSYS)做理論計算，並得到較好之結果，降低發光效率於高電流注入下將產生效率下降之情況。

In this thesis, we designed the epitaxial structure of InGaN light-emitting diodes (LEDs) to improve the carrier distribution, which could alleviate the efficiency droop behavior. We first designed a p-n pairs barrier for c-plane InGaN/GaN LEDs. The simulated results demonstrated that such p-n pairs barrier can effectively improve the carriers distribution in active region. Second, we designed LEDs with p-n pairs multiple quantum barrier in different position of multiple quantum well. The simulated results showed that the p-n pairs barrier LED in the fifth multiple quantum well exhibits an improvement in both droop behavior and radiative recombination, which is caused by more uniform carriers distribution and better spatial overlap between holes and electrons. Third, we decreased the thickness of quantum well nearby p-type GaN, and it would improve carrier transportation. The carrier distribution can become more uniform in the active region by using thin well structure. We can find out that the efficiency was drastically decreased when all quantum wells become thinner. However, by choosing part of quantum wells and decreasing the thickness of them, we can effectively improve the efficiency droop.