由於兼具透明與導電特性，氧化銦錫薄膜在光電產業中已經被廣泛地研究。氧化銦錫為寬能隙、n型高退化半導體，因而擁有低的電阻係數（2-4×10-4 Ωcm）。在薄膜成長時，錫雜質佔據氧空缺而形成退化半導體。根據以上特性，銦錫氧化物被廣泛地應用。在本實驗中，我們使用熱蒸鍍法在n型及p型氮化鎵薄膜（2-4um）上成長銦錫氧化物，並嘗試解決光電元件中發光強度及電流散佈間的衝突。根據實驗結果，我們將對於銦錫氧化物與氮化鎵的金屬接面，做深入的研究與探討。
近年來，光輔助溼蝕刻的建立增進了氮化鎵在室溫下之化學活性。經由紫外線照射，在半導體表面產生電子電洞對，並促進此電化學模型的氧化還原反應。在本實驗中，我們將n型氮化鎵置於氫氧化鉀溶液中，再使用氦鎘雷射進行光輔助溼蝕刻，並可得到300nm/min的蝕刻速率。

The GaN-based materials have successfully developed on short-wavelength laser diodes (LDs), light-emitting diodes (LEDs) and ultraviolet photodetector. Indium-tin-oxide (ITO) thin films have been studied extensively in the optoelectronic industry because they combine unique transparent and conducting properties. ITO thin film is a highly degenerate n-type semiconductor which has a low electrical resistivity of 2-4×10-4 Ωcm. The low resistivity value of ITO films is due to a high carrier concentration because the Fermi level (EF) is located above the conduction level (EC). The degeneracy is caused by both oxygen vacancies and substitutional tin dopants created during film deposition. Furthermore, ITO is a wide band gap semiconductor visible and near-IR region of the electromagnetic spectrum. Due to these unique properties, ITO has been used in a wide range of applications. In this study, we deposited InSnO film on n-type and p-type GaN by thermal evaporator to overcome the confrontation between brightness and current spreading in optoelectronic devices. According to the experimental results, we study the mechanisms and characteristics of InSnO on GaN.
Photoenhanced wet etching of GaN has recently been identified as a means of greatly improving the chemical reactivity of GaN at room temperature. Ultraviolet illumination is used to generate electron-hole pairs at the semiconductor surface, which enhance the oxidation and reduction reactions within an electrochemical cell. We have previously studied a photocnhanced wet etching process n-type GaN using HeCd laser illumination and KOH solution. In this study, etch rates of approximately 300nm/min were obtained.

CONTENTS I
LIST OF FIGURES III
ABSTRACT VI

CHAPTER1 INTRODUCTION 1
1.1 The Background of Research on III-Nitrides 1
1.2 Group-III Nitride Compund Semiconductors 3
1.3 The Application of Indium Tin Oxide 6
1.4 Room-Temperature Photoenhanced Wet Etching of n-GaN 8

CHAPTER2 EXPERIMENTS 11
2.1 MOCVD Growth System 11
2.2 Substrate Preparation of Sapphire 14
2.3 GaN Epilayer Growth Processes 14
2.4 Indium Tin Oxide Contacts produced by Thermal Evaporator 15
2.5 Sample Preparation of GaN/Sapphire 15
2.6 Indium Tin Oxide Thin Films produced by Liquid Phase
Deposition 16
2.7 Substrate Preparation of Silicon(100) 17
2.8 Room-Temperature Photoenhanced Wet Etching of GaN 17
2.9 Sample Preparation of GaN/Sapphire 18

CHAPTER3 RESULTS AND DISCUSSION 19
3.1 GaN Growth by MOCVD 19
3.1.1 Effect of Substrate Baking 20
3.1.2 Effect of Flow Rate of Ammonia 20
3.1.3 Effect of Flow Rate of TEGa 21
3.1.4 Temperature of Nitridation and Buffer 22
3.1.5 Effcct of Nitridation Time 23
3.1.6 Growth Time of GaN Buffer Layer 24
3.1.7 Growth Temperature of GaN Epilayer 25
3.1.8 Mechanism of DAP 26
3.2 Formation of InSnO Contact on n-GaN by Thermal
Evaporation 28
3.2.1 Effect of Annealing Temperature 29
3.2.2 Effect of Annealing Time 31
3.2.3 Annealing at Different N2/O2 Time Ratios 32
3.2.4 Flow Rate of Oxygen 33
3.2.5 Thickness of The Annealed InSnO 33
3.3 Formation of InSnO Contact on p-GaN by Thermal
Evaporation 35
3.3.1 Effect of Annealing Temperature 35
3.3.2 Effect of Annealing Time 36
3.3.3 Annealing at Different N2/O2 Time Ratios 38
3.3.4 Flow Rate of Oxygen 38
3.3.5 Thickness of The Annealed InSnO 38
3.4 Formation of InSnO Thin Film on silicon by Liquid
Phase Deposition (LPD) 40
3.4.1 Concentration of H2SnF6 41
3.4.2 Deposition Temperature 41
3.4.3 Concentration of Activator HNO3 42
3.4.4 Annealing Temperature and Annealing Time 42
3.5 Room-Temperature Photoenhanced Wet Etching of GaN 44
3.5.1 KOH Solution Concentration 45
3.5.2 Annealing Treatment 46

CHAPTER4 CONCLUSIONS 47

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