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標題: | 成長於偏鋁酸鋰基板上之氮化鎵的光學特性研究 Optical Properties of GaN Epitaxy on γ-LiAlO2 Substrate |
作者: | Fang-Chi Kou 郭芳旗 |
指導教授: | 張顏暉(Yuan-Huei Chang) |
關鍵字: | 氮化鎵,偏鋁酸鋰,光致螢光, GaN,LAO,PL, |
出版年 : | 2007 |
學位: | 碩士 |
摘要: | 本論文主要研究成長於偏鋁酸鋰(γ-LiAlO2)的基板上的氮化鎵薄膜與六角晶柱的光學性質。利用X光繞射及掃描式電子顯微鏡來確定樣品的結構與表面性質,再由光致螢光(PL)來比較不同成長因素的發光性質。
由X光繞射及掃描式電子顯微鏡的研究,我們得知樣品的表面為M-plane的GaN薄膜及C-plane六角晶柱的GaN混合結構,而由光致螢光光譜(PL)得到兩個主要的發光波峰位置,(1)C-plane六角晶柱的GaN發出3.367 eV;(2) M-plane薄膜的GaN發出3.51 eV。兩個波峰的相對發光強度隨著區域內的兩種結構比例而異。其中M-plane薄膜的GaN發出的光具有極性。而且分別可以得到不同的活化能,分別為EaM=11.7 meV,EaC=15.4meV In this thesis we investigate the optical properties of the M-plane GaN/C-plane GaN nano-crystal hetero-structures on γ-LiAlO2 substrate grown by plasma-assisted molecular beam epitaxy.In this structure, in addition to the M-plane epilayer, nanocrystals grown in c- direction could also be observed in the step edges of the M-plane GaN terra- ces and the hexagonal basis of the γ-LiAlO2 substrate. The photoluminescen- ce measurement was performed with a He-Cd laser, a monochromator and a closed cycle refrigerator. Two-peaks were observed in the PL spectra at low temperature. The peak at 3.367 eV is attributed to the emission from the C- plane GaN nanocrystals and the peak with polarization at 3,51 eV is attributed to the emission form M-plane GaN epi-layers. The relative intensity of these peaks is position dependent. In the area with higher concentration of the GaN nano-crystals the emission for the nanocrystals is stronger and vise verse. From the temperature dependent PL spectra it is found that the activation energy of the quenching of the PL in GaN nanocrystal is about 13.6-18.1 meV and this energy is attributed to the dissociation energy of exciton in GaN nanocrystal. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/30234 |
全文授權: | 有償授權 |
顯示於系所單位: | 物理學系 |
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