利用非極性/半極性氮化鎵基板製作氮化鎵垂直共振腔面射型雷射之研究

Abstract

本計劃主旨在於使用非/半極性氮化鎵基板成長高品質發光層並將之搭配高反射率之分佈式布拉格反射鏡製作出垂直共振腔面射型雷射並進一步探討其中光與物質間的強耦合作用產生的微共振腔極化子之現象。透過半/非極性氮化鎵的特性可以將現有的c軸氮化鎵量子井發光層惱人的量子侷限史塔克效應給降低並去除，此外，半極性氮化鎵(20-2-1)具有窄線寬的特性，對於在氮化鎵微共振腔中觀察到極化子特性有極大的潛力。若是以氮化鎵做磊晶成長的基板，更可以大幅提高磊晶的品質以及降低成長時產生的缺陷製作出高內部量子效率的發光層。垂直共振腔面射型雷射的共振腔屬於微共振腔的一種，可以在其中觀察到極化子的現象，若能藉由適當的設計，更可以利用極化子為波色子的特性達成室溫下的玻色愛因斯坦凝聚態以及極低閾值的極化子雷射。磊晶層的製作將搭配程式模擬先行優化磊晶層參數再行製作。製作完成的元件將搭配一系列的電致發光實驗來驗證使用非/半極性氮化鎵基板成長並製作出的垂直共振腔面射型雷射的優點以及特性。接著利用膜層傳遞矩陣及激子的羅倫茲模型理論模擬，來分析實驗上是否有觀察到極化子的現象。

The main effort of this project is to use non/semi-polar GaN substrates and high reflectivity distributed Bragg reflector to develop the GaN based vertical-cavity surface-emitting lasers (VCSELs) and microcavities exhibiting strongly coupled exciton-polaritons. The annoying quantum confined Stark effect (QCSE) in the traditional c-plane MQW can be reduced by growing quantum wells on the non/semi-polar GaN substrates, which will be beneficial to fabricate low threshold GaN-based VCSELs. Meanwhile, the emission polarization direction of the VCSELs can be easily specified. By using the GaN bulk as substrates, the epitaxial quality could be greatly improved and the defects could also be reduced, and the high quantum efficiency emission layers are expected. In addition, the cavity of the VCSEL is a kind of the MC, the bosonic quasi-particles, polaritons could be generated in such a MC emitter. It was recently reported that the narrow linewidth behavior was observed in (20-2-1) GaN MQW layer, which has great potential on achieving polaritons in the GaN microcavity (MC). By using the proper design, the Bose-Einstein condensation and ultra-low threshold polariton laser could be achieved by electrically injection at room temperature. Above mentioned epitaxial layer would be fabricated after simulation optimization to avoid additional cost on resources. By using the transfer matrix simulation and Lorentz oscillator model, the existence of strong coupled exciton-polaritons could be verified.