寬能隙材料半導體微共振腔之研究

Abstract

由於寬能隙半導體微共振腔在研究光與物質交互作用上十分具有潛力，因此近年來吸引許多研究群的研究與討論。此種半導體微共振腔可用以侷限光子與激子在微小空間中，進而產生一種同時具有光和物質特性的準粒子，一般稱之為共振腔極化子。此種準粒子具有玻色子的特性，包含了極小的有效質量與不需滿足庖立不相容原理的特性。這些特色導致了共振腔極化子可能被用於固態系統中達到室溫下的玻色-愛因斯坦凝聚。共振腔極化子被期望能夠達成一種極低臨界能量的新型態極化子雷射，這是一種不需要達到居量反轉即可產生雷射光的新元件。於此篇論文中，我們主要利用氧化鋅與氮化銦鎵材料製作微共振腔元件，並研究其極化子雷射與電激發極化子發光二極體的特性。 我們首先利用氧化鋅微共振腔元件成功在室溫下觀察到極化子雷射的現象，其達到雷射所需的臨界激發能量非常低。此外，我們更進一步觀察共振腔極化子釋放能量與凝聚的過程，在共振腔極化子釋放能量的過程中理論上所預期可能發生的現象，包含共振腔極化子瓶頸效應與玻色子的受激放射現象，這些效應皆在氧化鋅微共振腔的光學實驗中被觀測到。除此之外，我們亦實現了室溫下電激發氮化銦鎵極化子發光二極體，利用兩種不同的實驗技術，包含改變溫度的電激發光量測與改變收光角度的電激發光技術，我們同時觀察到共振腔極化子色散曲線的交錯現象，亦即證明了在室溫電激發的條件下，氮化鎵共振腔發光二極體確實存在光與物質交互作用的強耦合機制。這些研究成果再次證明了寬能隙半導體微共振腔是適合用來製作新一代共振腔極化子發光元件的重要材料。

Wide-bandgap semiconductor microcavities have attracted much attention in the research field of strong light-matter interaction in recent years owing to their potential to enhance and control the interaction between excitons and photons, which leads to cavity polaritons. This half matter-half light quasi-particle is characterized by the nature of Bose particles, including a very small in-plane effective mass and the lack of Pauli exclusion principle, resulting in the possible realization of room-temperature Bose-Einstein condensation in solids. Cavity polariton is expected to open the way for the development of a new generation of thresholdless polariton laser without the requirement of population inversion. In this thesis, we use ZnO-based and InGaN-based hybrid microcavities for the study of polariton lasing and electrically pumped polariton light-emitting diodes. We demonstrated a room-temperature polariton lasing with an extremely low threshold pumping density from the ZnO microcavity. The polariton relaxation mechanisms including polariton relaxation bottleneck effect and bosonic final state stimulation effect are experimentally demonstrated in this study as well. Furthermore, we present an electrically pumped InGaN-based polariton LED in strong coupling regime. Two different approaches including the temperature-dependent and angle-resolved electroluminescence spectra demonstrate an obvious polariton characteristic of anticrossing. These research results show that the wide-bandgap semiconductor microcavities are mostly adapted for the realization of a new generation of polariton emitters.