以光學方法分析發光二極體內不同厚度p-型氮化鎵層對底下氮化銦鎵/氮化鎵量子井發光效率的影響

Abstract

在本研究中，首先我們以氮化銦鎵半導體雷射 (406nm) 量測隨溫度變化的螢光頻譜、用 Ti:Sapphire 雷射之二倍頻 (波長391nm) 進行時域解析螢光頻譜、隨波長變化的時域解析螢光頻譜量測，以及量測電致發光頻譜和使用掃描式電子顯微鏡做陰極射線發光頻譜的量測，觀察不同樣品之量子井的特性並比較。透過優化高溫成長的p型氮化鎵厚度，我們最大化內部量子效率，並且在製作成氮化銦鎵/氮化鎵量子井發光二極體後減少它的電阻值．在成長p型氮化鎵鋁的電子阻隔層和p型氮化鎵層的過程中，量子井會因為高溫熱退火而使它重整銦聚集結構並達到加強載子局部化效果．除此之外，較弱的載子局部化會造成樣品有較低的內部量子效率． 在具有不同厚度的p型氮化鎵層的發光二極體樣品中，擁有最高的內部量子效率的樣品，同時也有最低的電阻值．具有較薄的p型氮化鎵層的發光二極體，它們的電阻值會容易受到量子井的品質影響．

In this study, we demonstrate the results of temperature-dependent photoluminescence, time-resolved photoluminescence, and wavelength-dependent TRPL, electroluminescence, and cathodoluminescence measurement results of the quantum wells of different samples. The optimization of the thickness of the high-temperature grown p-GaN layer for maximizing the QW internal quantum efficiency (IQE) and minimizing the device resistance in an InGaN/GaN QW light-emitting diode (LED) is demonstrated. During the growth of the p-AlGaN electron-blocking layer and p-GaN layer, the QWs are thermally annealed to first enhance carrier localization by reshaping the structures of indium-rich clusters before the optimized p-GaN thickness is reached. Beyond this point, the carrier localization effect becomes weakened, leading to lower IQE. Among the LED samples of different p-GaN thicknesses, the one with the highest IQE has the lowest device resistance. With a thicker p-GaN layer, the LED device resistance can be strongly affected by the QW crystal quality.