流量調制磊晶技術成長氮化銦的形貌與光性研究

Abstract

本論文提出由流量調制磊晶法（flow-rate modulation epitaxy，簡稱FME）成長的氮化銦奈米結構。在600℃利用流量調制磊晶法成長氮化銦時，三族和五族交替通入反應腔，且當通入三甲基銦反應氣體時加入250sccm的氨背景流量。我們利用原子力顯微鏡（AFM）、X光繞射分析(XRD)及光激螢光光譜（PL）的量測，研究氮化銦奈米粒的表面形貌與光學性質。實驗顯示當五族通入階段的氨流量小於1000sccm，會有滴狀金屬銦（In droplet）形成，且有較差的光學性質。而當氨流量大於1500sccm後，PL發光峰值位於0.75eV 而譜峰寬度約75 meV。除此之外，隨著增加五三比由10000增加至60000氮化銦成長速率維持不變，有別於傳統磊晶模式當五三比超過30000時成長速度下降至原先的1/4。我們認為利用流量控制磊晶法在高流量的氨環境下可以抑制氮原子形成錯位(stacking fault)，因此不但不會抑制氮化銦成長速度，發光強度亦不受氨流量增加而降低。

In this thesis, we proposed flow-rate modulation epitaxy （FME） to fabricate InN nanostructures. We use FME mode that an alternative supply of group-III and group-V sources to grow InN under 600℃, and growing under low background NH3 flows at 250 sccm during In step. Atomic force microscopy（AFM）, X-ray diffraction（XRD）and Photoluminescence（PL）measurements were used to investigate the morphology and optical properties of InN nanodots. Our experients show that In droplets were observed and the poor of optical qualities when NH3 flow rate below 1000 sccm at N-step. On the other III hand, stronger PL emission peaks at around 0.75 eV and linewidth about 75 meV is shown for NH3 flows higher than 1500 sccm. And FME growth mode is advantaged that no suppression of the growth efficiency even for V/III at 60000 is observed in comparison with published results using conventional mode that 75 % of growth rate is reduced once V/III larger than 30000. Together with the sustained photoluminescence efficiency, which peaks at 0.75 eV, this result reveals that FME suppresses the formation of stacking faults of nitrogen atoms under high V/III ratio regime.