氮化銦鎵/氮化鎵奈米結構之穿透式電子顯微術硏究

Abstract

在本研究的第一部份，我們以高解析穿透式電子顯微鏡術，研究四片氮化銦鎵/氮化鎵多重量子井發光二極體樣品的奈米結構。以預施應力方式成長的樣品，在成長高濃度的量子井結構前，先成長一層低濃度(約7%)之量子井，對其上的氮化鎵磊晶層造成一個拉張的應力。我們利用穿透式電子顯微術及應力分佈分析軟體分析這四片樣品的奈米結構。由穿透式電子顯微術所得到的影像，我們可以觀察到量子井內銦原子聚集及分佈不均勻的現象。透過應力分布分佈軟體去計算量子井內的平均濃度及銦原子濃度的變化範圍，我們發現在以預施應力成長的樣品中，量子井內的銦濃度的變化範圍較小。 在本研究的第二部份，我們比較兩片成長在以陽極氧化鋁製作的二氧化矽奈米孔洞模板上的氮化鎵奈米柱的結構。從掃描式電子顯微鏡及穿透式電子顯微鏡的影像中發現，我們成功地以二氧化矽奈米孔洞模板長出氮化鎵奈米柱，而且奈米柱的品質良好。

In this research, first the nanostructures of four InGaN/GaN mquantum-well (QW) light-emitting diode samples are studied with high resolution transmission electron microscopy (HRTEM). In the prestrained samples, a low-indium InGaN/GaN QW (~7% indium) is grown for creating a tensile strain in the barrier layer right above it before high-indium InGaN/GaN QWs are deposited. We use the techniques of HRTEM and strain state analysis (SSA) to analyze the nanostructures of these four samples. From the HRTEM images, one can see different degrees of indium aggregation and composition fluctuation between QWs. From the SSA calibrated average indium content and SSA calibrated indium composition fluctuation, we find the carrier localization effect is shown to become weaker in the sample, which was grown with prestrained growth technique. Then, we compare the nanostructures of two samples of overgrown GaN nanocolumns on a porous SiO2 template which is fabricated using anodized aluminum oxide (AAO) as an etching mask. From the scanning electron microscopy and the transmission electron microscopy images, we find that we can grow the GaN nanostructure on the template, and the quality of GaN nanocolumns is good.