氮化銦量子點與薄膜之光激發螢光研究

Abstract

本論文利用原子力顯微鏡與光激發螢光光譜來探討氮化銦量子點 與薄膜樣品的表面形貌與光學特性。在改變成長溫度下，以流量調制 磊晶法 (flow-rate modulation epitaxy，簡稱 FME )與傳統有機金屬氣相沉積 ( metalorganic chemical vapor deposition，簡稱 MOCVD )模式成長的量子點密度會隨著成長溫度上升而下降。此外以MOCVD模式成長的量子點，因為受到大量來自NH3的氫氣影響，造成其成長速率降低。而成長溫度也是影響量子點的載子濃度，PL光譜峰值與發光效率的一個重要參數。以FME成長模式成長的量子點，其背景氨流率不但可以控制樣品的形貌，同時影響其發光特性。最後利用free-to-bound理論模型，我們推估量子點內載子濃度，並驗證電洞的能量分佈主導光譜峰值隨環境溫度的變化。

InN dot density grown by flow-rate modulation epitaxy ( FME ) and metalorganic chemical vapor deposition ( MOCVD ) exhibited reduction with increasing growth temperature. Moreover, the InN dot growth rate in MOCVD mode was less that in FME mode. Growth temperature affected the carrier concentration, PL peak energy, and emission efficiency of InN dots. In FME mode, NH3 background flows controlled not only the morphology but also the emission property of InN dots. The lineshape model based on free-to-bound recombination was used to simulate the PL spectra and estimate the carrier concentration of InN dots and films. We demonstrated that the PL peak energy was governed mainly by energy distribution of holes at different environmental temperatures.