等電子價位銦摻雜氮化鎵薄膜之光激光及拉曼光譜研究

Abstract

為了探討等電子價位銦摻雜對氮化鎵薄膜特性的影響，我們在不同溫度，不同Trimethy1 Indium (TmIn) 流量，及不同緩衝層度下成長摻雜銦所氣鎵膜並以光激光，拉曼光譜及霍爾量測分析銦的溶入所造成的效應，由實驗結果我們發現，配合長晶溫度；緩衝層厚度；適當的控制銦的摻入量，會有效的降低因缺陷所造成的背景載子濃度及和深能階有關的激光，此外束縛激子躍遷所造成之光激光的半高寬也有變窄的現象，經分析，我們發現此半高寬和背景載子濃度之平方根正比，此關係可由一簡單的缺陷隨機分佈模型予以解釋並可估算缺陷的屏蔽半徑以推測缺陷的屬性，比較近能隙發光對黃光的強度比值和背景濃度的關係，此種缺陷應屬於所謂的補償中心，由拉曼光譜的實驗結果，我們發現銦的摻入對E2模的位置會有所影響，顯示銦原子的加入改變了晶體內部的缺陷密度進而改變了薄膜內部的應變，此應變是由缺陷造成的靜流力應變，此外，我們將討論變溫光激光及高TMIn流量下所造樣品不均勻的現象。

In order to investigate the effect of isoelectronic doping on the properties of GaN, In-doped GaN films grown at various temperatures, with different TrimethylIndium (TMIn) flow rates and buffer layer thicknesses were prepared and studied by Photoluminescence (PL), Raman scattering and Hall measurements. The experimental results show that under certain conditions. In-doping is effective in reducing the undesired background concentration, deep-level related emissions and line width of near band edge (NBE) emission. The analyses of our results suggest an interesting correlation between the FWHM of NBE emission and background concentration. A model based on the random distribution of defects seems to be useful in interpreting the correlation. The dependence of the intensity ratio of NBE to deep-level transition indicates that the defects accounting for the yellow luminescence should be of compensating center. From Raman spectra, the position of E2 mode and the appearance of A1(TO) and E1(TO) modes all change with the Inincorporation indicating the strain variation in the GaN thin film. The imperfect hexagonal structure appears to be improvable to some extent by In-doping. Besides, temperature dependent PL spectra and nonuniform surface occurred under high TMIn flow rate will also be discussed.