氮化鎵面射型雷射及微共振腔元件之研究

Abstract

本論文主要是探討氮化鎵面射型雷射及微共振腔元件之設計、製作及其發光特性。我們首先利用模擬軟體進行複合式結構的氮化鎵面射型雷射之設計。接著，我們利用有機金屬氣相沉積系統成長具高反射率氮化鎵/鋁化鎵布拉格反射鏡之3λ氮化鎵系結構，並在此結構上以電子槍蒸鍍機蒸鍍高反射率之介電質反射鏡以完成面射型雷射結構之製作。針對此一結構我們在室溫下以光激發操作時，已觀察到雷射發光的現象，其臨界激發光能量密度為53 MJ/cm2 ，雷射光波長為448nm。此外我們亦針對此雷射之特性做了更深入之探討，諸如：發散角、極化程度、不同操作溫度之影響等…，經由實驗結果得知，我們已成功的製作出光激發氮化鎵面射型雷射。同時，我們亦針對此一結構導入製程以研發氮化鎵微共振腔元件。在充分運用各種半導體製程技術下，諸如：蝕刻、薄膜成長、歐姆接觸電極之蒸鍍等…，我們也成功的製作出氮化鎵微共振腔元件。此一元件在室溫20毫安培的電流注入下，發光波長在458.5nm，並具有一窄的光譜半高寬值為6.7nm。此外我們也針對此元件與一般的發光二極體及具下反射鏡之發光二極體元件做變溫操作及變電流操作之發光特性比較，亦發現氮化鎵微共振腔元件具有較佳的波長穩定性。此元件之特性說明了其結構及製程在發展電激發氮化鎵面射型雷射之可行性與潛力。

In this thesis, we report the design, fabrication and emission characteristics of GaN-based VCSEL and GaN-based MCLED. We grew the 3λ nitride-based structure with 25 pairs of AlN/GaN DBR by MOCVD, and then deposited 8 pairs of Ta2O5/SiO2 DBR by E-gun deposition to complete the full structure of GaN-based VCSEL. The fabricated structure was optically pumped at room temperature and the laser emission was observed. The threshold pumping energy was about 53 MJ/cm2 and the laser emission peak wavelength was about 448nm. It’s evidently that we have successfully fabricated the optically pumped GaN-based VCSEL. Besides, we also discuss the characteristics of optically pumped GaN-based VCSEL such as excitation energy - emission intensity curve (L-I), near field pattern (NFP), far field pattern (FFP), threshold carrier density (Nth), threshold gain(gth), degree of polarization (DOP), temperature dependent threshold and characteristic temperature (T0). We also fabricated the GaN-based MCLED following the success of optically pumped GaN-based VCSEL. The device showed the emission wavelength of 458.5nm and the narrowed spectral FWHM of 6.7nm at 20mA injected current. The MCLED also showed stable emission peak wavelength, while varying the injected current density and operating temperature. It indicated that a good resonant cavity was fabricated. Such MCLED could be the basis for electrically injected GaN-based VCSEL.