氮化鎵奈微米共振腔發光元件研究

Abstract

本篇論文旨在探討共振腔長在數個微米至奈米的氮化鎵發光元件的製程技術及設計原理。以期能夠成功製作出電激發氮化鎵面射型雷射及奈米雷射。 首先，透過在量子井上成長氮化鋁，做為混合式布拉格反射鏡氮化鎵微共振 腔結構的電流阻擋層，取代過去只有成長氮化矽在在 p 型氮化鎵上做絕緣層的 方法，以期達到更加的電流侷限效果以及側向的光學侷限。更設計了環型的透明 導電層取代原先的圓型透明導電層，希望能減少共振腔內部的損耗。接著，由於考慮到了藍寶石基板本身的電導率和熱傳導率不佳，以及氮化鎵-氮化鋁布拉格反射鏡的製作控制困難。我們採用了雷射剝離技術製作雙介電質布拉格反射鏡搭配氮化鋁電流阻擋層的電激發微共振腔發光元件。在元件複雜的製作完成之後，我們量測元件得到了一個高(800)以上的共振腔品質因子，並量測到了光激發雷射操作以及橫向模態，雖然沒有達到電激發雷射操作，但確實證明了此種設計製作的可行性，並且在最後提出元件可改良以及最佳化的方向。 第二部分，我們採用波導理論及有限元素分析法模擬設計了一個奈米雷射結構，證明了金屬能加強對光場局限的能力提升奈米級半導體元件的表現。

The purpose of this thesis is to discuss the design rules and improvement on the process of GaN-based micro/nano cavity light emitting devices so that we can successfully fabricate a laser lift-off GaN-based VCSELs and GaN-based nanolaser. At first, we formed a GaN microcavity of hybrid Bragg reflector with a current blocking layer by growing AlN on the quantum well instead of growing SiN on the p-GaN conventionally in order to achieve a better current confinement and lateral optical confinement. Additionally, we designed a ring-shape transparent contact layer in replace of the original round-shape one to reduce the internal loss of the resonant cavity. To modify the intrinsic property of the sapphire substrate (poor electric and thermal conductivity) and to overcome the difficulty in the process of the AlN/GaN DBR, we used the laser lift-off technique to fabricate a MCLED with two dielectric DBRs and an AlN current blocking layer. After the complicated fabrication process, we obtained a high Q factor (800) and transvers modes from the device of laser operation by optically pumped. Even though we did not achieve the laser operation by electrically pumped, we have proved the feasibility of this method and gave some suggestion to improve and optimize the fabrication. Second, we design a nanolaser by using finite element method and circular waveguide theory, the results prove that metal can enhance optical confinement and improve the performance of nanolaser.