規則排列氮化銦鎵/氮化鎵量子井奈米柱陣列生長及特性分析

Growth and Characterization of Regularly Patterned InGaN/GaN Quantum-well Nanorod Arrays

廖哲浩(Che-Hao Liao)

指導教授 ： 楊志忠

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.02101

摘要

在本論文中，首先我們報告利用有機金屬氣相沉積法於c平面藍寶石基板上成長不同截面大小與間距的高晶體品質氮化鎵奈米柱。藉由奈米壓印技術及流量調變磊晶方法來達成選區成長效果，形成週期性、結構一致的氮化鎵奈米柱。
接下來，我們於規則排列的氮化鎵奈米柱上成長氮化銦鎵/氮化鎵量子井結構，可同時於奈米柱頂端形成具極性的c平面圓盤狀量子井結構以及奈米柱側壁形成非極性的m平面量子井結構，形成外層包覆量子井的奈米柱結構。為了分析這兩種量子井結構的形貌及組成，我們使用掃描式電子顯微術、陰極射線致發螢光光譜及影像分析、穿透式電子顯微術及應力狀態分析軟體來觀察及分析。應力狀態分析軟體能夠分析穿透式電子顯微鏡影像，提供我們關於量子井細部結構及組成等資訊。分析結果發現側壁m平面量子井較頂端c平面量子井的寬度窄但銦含量較高。同時，單就側壁m平面量子井而言，側壁量子井寬度隨著奈米柱高度增加而遞減，而側壁量子井的銦含量卻是隨著奈米柱高度增加而遞增。這個結果顯示組成量子井的原子是沿著奈米柱側壁由底部往頂部遷移。
然後，我們以奈米壓印製作不同直徑大小與間距的孔洞陣列，並於其上成長不同高度的氮化鎵奈米柱及相同成長條件的氮化銦鎵/氮化鎵量子井結構，因而形成了不同的截面結構。氮化鎵奈米柱的截面寬度大小主要與奈米壓印孔洞的直徑大小有關，而與奈米柱的高度及間距關係較小；另一方面，氮化銦鎵/氮化鎵量子井結構之截面厚度卻與奈米柱的高度極為相關，且稍微受到奈米柱的六角排列型式影響。
氮化鎵奈米柱的截面寬度大小變化能夠以自組成催化劑的鎵球三維立體比例的物理性質來描述，而氮化銦鎵/氮化鎵量子井的截面厚度變化則是需由相鄰奈米柱間能讓成份原子進入的間隙體積來解釋。此外，對於不同直徑、間距、高度及六角排列型式的奈米柱量子井，量測其俯視、截面及就單根奈米柱量子井局部區域打點的陰極射線螢光光譜分析結果，發現發光波長隨著奈米柱高度降低、奈米柱截面寬度增加或奈米柱間距增加而變長，且奈米柱六角排列型式以邊對邊的組合會比角對角的組合發光波長要長。

關鍵字

奈米柱 ； 氮化鎵 ； 氮化銦鎵 ； 規則排列 ； 奈米柱陣列 ； 生長 ； 磊晶

並列摘要

In this dissertation, we first demonstrate the growth of high-quality GaN nanorods (NRs) on c-plane sapphire substrate by metalorganic chemical vapor deposition with various hole patterns on the templates. With the nano-imprint technique, the selective-area growth leads to the growth of regularly patterned GaN NRs. The growth of GaN NRs starts with a hole-filling process, followed by NR growth with the pulsed growth mode through switching on and off alternatively the TMGa and NH3 flows. Regularly arranged GaN NRs of uniform geometry are formed.
Then, a regularly-patterned, c-axis nitride NR array of quite uniform geometry with simultaneous depositions of top-face, c-plane disc-like and sidewall, m-plane core-shell InGaN/GaN quantum well (QW) structures is formed. The differences of geometry and composition between these two groups of QW are studied with scanning electron microscopy, cathodoluminescence (CL), and transmission electron microscopy (TEM). In particular, the strain state analysis results in TEM observations provide us with the information about the QW width and composition. It is found that the QW widths are narrower and the indium contents are higher in the sidewall m-plane QWs, when compared with the top-face c-plane QWs. Also, in the sidewall m-plane QWs, the QW width (indium content) decreases (increases) with the height on the sidewall. The observed results can be interpreted with the migration behaviors of the constituent atoms along the NR sidewall from the bottom.
Next, the cross-sectional sizes of the GaN NRs and QW NRs of different heights and different hexagon orientations between different hole patterns, including different hole diameters and pitches, are demonstrated. The cross-sectional size of the GaN NRs is controlled by the hole diameter and has little to do with the NR height and pitch. On the other hand, the cross-sectional size of the QW NRs is mainly determined by the NR height and is slightly affected by the hexagon orientation. The cross-sectional size variation of GaN NRs is interpreted by the three-dimensional nature of the formed catalytic Ga droplet. The cross-sectional size variation of QW NRs is explained by the condition of constituent atom supply in the gap volume between the neighboring NRs. Also, the plan-view and cross-sectional CL emission wavelengths, including the whole scale and local measurements, among those samples are compared. The emission wavelength depends on the NR height, cross-sectional size, pitch of the pattern, and hexagon orientation. It involves in the factors of indium incorporation rate and well layer thickness and shows a complicated combination of various affecting factors. Generally speaking, the QW NRs with a shorter QW NR, a larger cross-sectional size, or a larger pitch have a longer emission wavelength. The NRs with the side-by-side hexagon orientation have longer emission wavelengths, when compared with those with the edge-to-edge hexagon orientation.

並列關鍵字

Growth ； Regularly Pattern ； InGaN ； GaN ； Nanorod ； Array ； Nanowire ； Nano cclumn

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