Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes
碩士 === 國立交通大學 === 電子研究所 === 98 === Based on semiconductor light-emitting diodes, solid state lighting is a promising approach for the realization of highly efficient white light sources. The Group-III nitrides materials provide a great potential of constructing the multiple quantum wells which...
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ndltd-TW-098NCTU54281432016-04-18T04:21:46Z http://ndltd.ncl.edu.tw/handle/39642401612167539100 Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes 應用於非極性氮化鎵發光二極體元件以改善光萃取效率的極性選擇化學蝕刻 Chuang, Kai-Lin 莊凱麟 碩士 國立交通大學 電子研究所 98 Based on semiconductor light-emitting diodes, solid state lighting is a promising approach for the realization of highly efficient white light sources. The Group-III nitrides materials provide a great potential of constructing the multiple quantum wells which can emit light in blue and UV region and be used as important sources of white lighting. However the asymmetry of the Group-III nitrides materials crystalline structure leads to an undesirable Quantum-Confined Stark Effect (QCSE) which is a barrier of the recombination of electrons and holes. Besides, guiding the emission light out of the devices is one another important issue for it determining the total lighting efficiency by light extraction efficiency. In this thesis, the epitaxial growth of nonpolar a-plane GaN on trench-patterned m-plane sapphire and on trench-patterned a-plane GaN template with r-plane sapphire by MOCVD was performed. The experimental knowledge was first constructed on the growth mode of a-plane GaN on trench-patterned m-plane sapphire and then applied to a modified technique, trench epitaxial lateral overgrowth (TELOG) on trench-patterned a-plane GaN template with r-plane sapphire, and successfully gain the planar a-plane GaN and the corresponding InGaN/GaN MQWs on it. The critical growth methods, i.e. the low level of V/III ratio of ~100, growth mode, i.e. the +c-direction-dominated growth fronts, crystalline quality, i.e. dislocation density decreasing from 1E10cm-2 to 1E8cm-2 at lateral wing region, optical properties including photoluminescence (PL) and cathodoluminescence (CL) are observed in this thesis. A chemical etching technique based on the KOH solution was applied to the TELOG a-plane GaN and InGaN/GaN MQWs. The etching conditions including the temperature between 100°C and 140°C, the concentration of KOH between 5 wt. % and 20 wt. % and the etching times: 10min, 20min, 40min, 80min and 160min. This integration provides air-voids with specific geometries, i.e. the isosceles triangle or trapezoid or the mixed one, in the nonpolar a-plane GaN. Under investigations, it provides great improvement of the light extraction ability at a wide range of direction. Based on the varied-angle PL measurement, an approximately 3 times enhancement of the PL intensity was achieved at the angle from 25° to 50° with respect to the normal direction of the sample surface. Furthermore, by the combination of the etching mechanisms and the techniques of substrate engineering, a possible chemical lift-off process is expected to be established. The thesis provides an integrated process includes the fabrications of nonpolar a-plane GaN materials by TELOG and the etching procedures by KOH solution without extra damages, which would be a powerful solution to enhance the total lighting efficiency from the factors of internal quantum efficiency and the light extraction efficiency at a same time. Chang, Chun-Yen 張俊彥 2010 學位論文 ; thesis 136 en_US |
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碩士 === 國立交通大學 === 電子研究所 === 98 === Based on semiconductor light-emitting diodes, solid state lighting is a promising approach for the realization of highly efficient white light sources. The Group-III nitrides materials provide a great potential of constructing the multiple quantum wells which can emit light in blue and UV region and be used as important sources of white lighting. However the asymmetry of the Group-III nitrides materials crystalline structure leads to an undesirable Quantum-Confined Stark Effect (QCSE) which is a barrier of the recombination of electrons and holes. Besides, guiding the emission light out of the devices is one another important issue for it determining the total lighting efficiency by light extraction efficiency.
In this thesis, the epitaxial growth of nonpolar a-plane GaN on trench-patterned m-plane sapphire and on trench-patterned a-plane GaN template with r-plane sapphire by MOCVD was performed. The experimental knowledge was first constructed on the growth mode of a-plane GaN on trench-patterned m-plane sapphire and then applied to a modified technique, trench epitaxial lateral overgrowth (TELOG) on trench-patterned a-plane GaN template with r-plane sapphire, and successfully gain the planar a-plane GaN and the corresponding InGaN/GaN MQWs on it. The critical growth methods, i.e. the low level of V/III ratio of ~100, growth mode, i.e. the +c-direction-dominated growth fronts, crystalline quality, i.e. dislocation density decreasing from 1E10cm-2 to 1E8cm-2 at lateral wing region, optical properties including photoluminescence (PL) and cathodoluminescence (CL) are observed in this thesis.
A chemical etching technique based on the KOH solution was applied to the TELOG a-plane GaN and InGaN/GaN MQWs. The etching conditions including the temperature between 100°C and 140°C, the concentration of KOH between 5 wt. % and 20 wt. % and the etching times: 10min, 20min, 40min, 80min and 160min. This integration provides air-voids with specific geometries, i.e. the isosceles triangle or trapezoid or the mixed one, in the nonpolar a-plane GaN. Under investigations, it provides great improvement of the light extraction ability at a wide range of direction. Based on the varied-angle PL measurement, an approximately 3 times enhancement of the PL intensity was achieved at the angle from 25° to 50° with respect to the normal direction of the sample surface. Furthermore, by the combination of the etching mechanisms and the techniques of substrate engineering, a possible chemical lift-off process is expected to be established.
The thesis provides an integrated process includes the fabrications of nonpolar a-plane GaN materials by TELOG and the etching procedures by KOH solution without extra damages, which would be a powerful solution to enhance the total lighting efficiency from the factors of internal quantum efficiency and the light extraction efficiency at a same time.
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author2 |
Chang, Chun-Yen |
author_facet |
Chang, Chun-Yen Chuang, Kai-Lin 莊凱麟 |
author |
Chuang, Kai-Lin 莊凱麟 |
spellingShingle |
Chuang, Kai-Lin 莊凱麟 Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
author_sort |
Chuang, Kai-Lin |
title |
Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
title_short |
Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
title_full |
Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
title_fullStr |
Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
title_full_unstemmed |
Integration of Nonpolar A-Plane Gallium Nitride Fabricating and Chemical Etching Processes for Lighting Efficiency Enhancement of Light-Emitting Diodes |
title_sort |
integration of nonpolar a-plane gallium nitride fabricating and chemical etching processes for lighting efficiency enhancement of light-emitting diodes |
publishDate |
2010 |
url |
http://ndltd.ncl.edu.tw/handle/39642401612167539100 |
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