同時以光激發及電激發法研究量子點之載子動力學

Study of carrier dynamics in quantum dots under simultaneous optical and electrical excitation

鄭瑋霖(Wei-Lin Cheng)

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(2009年)

https://doi.org/10.6342/NTU.2009.00840

摘要

在本論文中，我們同時使用光激發及電激發法來探討量子點中的載子動態。利用電激發的方式達成調控樣品中載子填滿率的目的，再同時輔以光激發進行動態實驗的量測，探討不同載子填滿率對載子動態所造成之影響。我們使用的樣品為五層量子點結構，利用黃光製程所製作的「傾斜型開窗光放大器結構」進行量測。
在高強度光激發時，由於瞬間載子數量太過龐大，造成瞬間打入高能階的載子數量相對提高，我們可以利用具時間解析之單光子計數(time correlated single photon counting, TCSPC)量測架構探討高低能態間的載子鬆弛效應，同時也在時間軸上觀察到載子的補充現象。
接著將會引入載子複合機制隨激發強度不同而有所差異的這項討論。藉由在電激發的情況下，由一連串改變灌注電流的實驗，觀察到載子複合發光機制的轉變。
在較弱的灌注電流下，基態及激發態的趨勢相同，衰減時間皆隨著灌注電流上升而下降。而在較強的灌注電流下，對基態而言，時間常數呈現定值；但對激發態而言，時間常數則會隨著電流上升而變長。
我們使用的樣品為DO1128五層量子點結構，利用黃光製程所製作的「傾斜型開窗雷射結構」進行量測。

關鍵字

光激發 ； 電激發 ； 單光子計數 ； 載子鬆弛 ； 複合機制 ； 載子填滿率

並列摘要

In this thesis, simultaneous optical and electrical excitation is used to study the carrier behaviors of quantum dots. Electrical excitation, serving the purpose of controlling the carrier occupation probability, is used in conjunction with optical excitation to determine the relations between the occupation probability and carrier dynamics. The sample studied in this thesis is a five-layer quantum-dot optical amplifier with tilted facets and windowed stripe on top metal contact.
Under high excitation conditions, the instantaneous carrier injection results in a sudden increase in the number of excited carriers captured into higher energy states. Using the time correlated single photon counting (TCSPC) setup, carrier relaxation between energy states can be observed as well as the effect of carrier replenishing.
Next, the dependence on excitation intensity that determines the recombination mechanisms of carriers is studied. Exploiting this dependence on excitation intensity, electrical excitation is used to investigate the change in carrier recombination mechanisms by varying injection current.
Under low current injection, the ground state and excited states exhibit similar trends of decreasing decay time as injection current is increased. At a higher current injection, however, the ground state demonstrates an injection-independent time constant as opposed to the behavior of the excited state where its time constant increases as current injection increases.
The sample studied for this thesis is a five-layer quantum dot (DO1128) “Tilted Windows Laser Structure”.

並列關鍵字

optical excitation ； electrical excitation ； TCSPC ； carrier relaxation ； recombination mechanisms ； occupation probability

參考文獻

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