由有機金屬化學氣相沈積成長不同長晶溫度之氮化銦奈米點的光學與形貌特性研究

Abstract

由流量控制法（flow-rate modulation epitaxy，FME）成長在550 oC到725 oC的氮化銦奈米點，利用光激螢光光譜（PL）與原子力顯微鏡（AFM）的量測，研究氮化銦奈米點的光學性質與表面形貌。由AFM與X光光譜的分析，指出在長晶溫度低於575 oC時，有滴狀金屬銦（In droplet）形成，這是被歸因為在低溫下氨的分解效率低落所致。而當長晶溫度大於675 oC時，氮化銦的成長率快速下降，我們認為在這長晶的區域內有銦原子的脫逸（In desorption）效應產生。在光學的部分，我們發現滴狀金屬銦的形成，總伴隨著光學性質的惡化。而在長晶溫度大於600oC沒有形成滴狀金屬銦的樣品上，則可以看到較好的光學性質。所對應到的光譜峰值能量（peak energy ∼0.76eV）幾乎不隨長晶溫度改變，而光譜的半高寬隨著溫度的上升也只有些微的從∼71增加到∼74 meV。此外我們也作了變溫光激螢光光譜的量測，發現成長在675∼725 oC的氮化銦奈米點樣品有14∼20meV的紅移，這代表我們在高溫成長的氮化銦樣品有很好的品質。

Photoluminescence（PL）and atomic force microscopy（AFM）measurements were used to investigate the optical properties and morphology of InN nanodots prepared by flow-rate modulation epitaxy at 550∼725 oC. In droplets were observed for samples grown at temperatures <575oC, as confirmed by both AFM and X-ray diffraction measurements, which can be attributable to the poor cracking efficiency of ammonia at this temperature range. Nevertheless, as the growth temperature is higher than 675oC, rapid declination in growth efficiency. It suggests that desorption of In adatom occurs at such a growth region instead. Concerning the optical properties, it is found that once the In droplets are formed, the optical properties of InN dots deteriorate significantly. As for droplet-free samples grown at temperatures □600 oC, good luminescence properties are obtained. The corresponding PL peak energy is nearly independent（∼0.76 eV）of growth temperature, accompanied by a slight linewidth variation from 71 to 74 meV as the temperature varies from to . Furthermore, we also conducted temperature-dependent PL measurement. A clear redshift of 14∼20 meV were found in InN nanodot samples prepared at 675∼725 oC, suggesting good quality of our high-temperature InN samples.