受應力分佈的氮化銦鎵薄膜之載子動力學

Abstract

本論文研究以有機金屬化學氣相沉積系統於不同成長溫度(675-750 oC)所成長一系列之氮化銦鎵薄膜，其銦含量介於(x=0.38-0.18)。根據X光倒置空間圖 (RSM)分析，發現當成長溫度高於700 oC時，薄膜會出現受應力與鬆弛狀態的兩種相位。透過時間解析光譜發現，不論是受應力或鬆弛狀態下的薄膜，其時間衰減曲線都需以自然衰減函數加上一個扭曲 (stretched) 指數衰減函數擬合。藉由扭曲參數(β)的分佈可得知，當薄膜處於鬆弛狀態時 (β=0.6-0.8)，其侷限態效應比受應力的薄膜 (β=0.9-1.0) 明顯。藉由變溫的螢光光譜及時間解析光譜，發現鬆弛狀態下的氮化銦鎵薄膜，有較高的內部量子效率及較強的侷限效應。最後，我們歸納出鬆弛狀態下的氮化銦鎵薄膜因為侷限態效應而使得其發光效率較為佳。

InxGa1-xN films (x=0.38-0.18) grown at different temperatures (675-750 oC) by metalorganic chemical vapor deposition (MOCVD) are investigated. From X-ray reciprocal space mapping (RSM), InGaN films grown at temperatures higher than 700 oC are found to have double phases, containing strained and relaxed phases. Time-resolved PL (TRPL) studies indicate that both the PL peaks of strained and relaxed phases shows nonexponential decay trace, which should be fitted by stretched exponential decay shape. According to the stretched parameters (β), localization effect is found to be more pronounced in relaxed phase. Temperature dependent PL intensity and lifetime also reveal a higher internal quantum efficiency and a stronger localization in relaxed phases. We conclude that the higher internal quantum efficiency in relaxed films is due to the localization effects.