光激發與電注入式量子點微碟雷射之製作與量測

Fabrication and Measurement of Optically Pumped and Current-injected Quantum-dot Microdisk Lasers

謝懷陞(Huai-Sheng Hsieh)

指導教授 ： 毛明華

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01610

摘要

採用HBr濕式蝕刻取代易破壞表面的ICP-RIE乾式蝕刻，並精準地控制HF蝕刻的時間，能成功地將微碟中，屬於徑向模態數大於2的模態有效抑止。我們成功地做出直徑3.1μm的微碟結構，並且最高能發出雷射光的溫度為200K，且最低有效臨界激發強度約為146μW（溫度140K）。隨著溫度改變，臨界激發強度並不是單調地變化，在溫度140K下，其臨界激發強度最低；我們也發現斜率效率與臨界激發強度呈反向變化。溫度的變化也會影響量子點主要發光波長，其變化率 約為0.21nm/K，這能合理解釋在不同的溫度下能激發出不同的模態；我們還可以觀察到模態的位置亦會隨著溫度稍稍移動，變化大小 約為 ，以此數據做理論計算得到等效折射率隨溫度的變化大小 約為 。
在較小微碟量測方面，在溫度78K下，能發出雷射的最小微碟直徑為2.2μm，其臨界激發強度約為479μW。比較微碟直徑3.1μm與2.2μm的模態間距，分別為30nm與36nm，這與我們模擬徑向模態數為1的模態相符合。
在電注入激發微碟的研究上，我們利用BCB作平坦化，可以做出可供量測的樣品，但無法看到頻譜上有模態出現，合理推論可能是由於最近ICP-RIE之乾式蝕刻機台不穩定，破壞微碟結構所造成的。

關鍵字

微碟 ； 電注入 ； 光激發

並列摘要

We have achieved lasing in InGaAs quantum-dot (QD) embedded GaAs microdisks (MDs) under optical pumping. The whispering-gallery-modes (WGMs) of radial number over 2 in the MD cavity were perfectly reduced by finely controlled HF-based wet-etched time. The MD was successfully fabricated by HBr-based wet-etching process in place of ICP-RIE dry-etching, which would destroy the surface smoothness of MDs. For the D=3.1μm MD, we demonstrated lasing behavior at the highest temperature of 200 K, and the minimum threshold is about 146μW (140K). The temperature dependence of lasing threshold does not change monotonously, and the minimum threshold occurred at 140K. We also find that the tendency of lasing threshold and slope efficiency is generally opposite. The main peak photoluminescence of QDs was shifted with varying temperature at the speed of = 0.21 nm/K which can be applied to explain the favored lasing mode at each temperature respectively. The lasing mode was shifted at the speed = due to index changed, and the temperature dependence of index is about = .
At 78K, we demonstrated the 2.2-μm-diameter MD lasing and the threshold is about 479μW. For the 3.1-μm and 2.2-μm-diameter MDs, we observed the WGMs with mode spacing 30nm and 36nm respectively, which agree very well with our simulation results.
We used BCB for planarization and fabricated the current-injected MD structure, but have not observed any mode yet. It might be caused by ICP-RIE process, which was instable recently and may have destroyed the MD structures.

並列關鍵字

microdisk ； injection ； temperature dependence

參考文獻

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