鍺量子點在氮化矽中的形成機制與鍺量子點可見光光二極體的研製

Placement of Ge quantum dots in silicon nitride substrate and realization of Ge quantum dots visible-light photo-diodes

張宇瑞(Yu-Jui Chang)

指導教授 ： 李佩雯

國立中央大學/資訊電機學院/電機工程學系/碩士(2011年)

摘要

本論文利用選擇性氧化在二氧化矽或氮化矽絕緣層上之複晶矽鍺結構的方法將鍺量子點置放於二氧化矽或氮化矽等不同的介質環境中。因此，我們不僅可以控制鍺量子點本身的大小，也可以調變量子點周圍的介質環境，進一步改變了鍺量子點的電子能結構。此外，量子點的大小及結晶性也會受到周圍的介質環境不同而被影響。
利用鍺量子點自身所誘發的氮化矽局部氧化效應，我們成功地將鍺量子點置於氮化矽介質層中。透過穿透式電子顯微鏡（TEM）與能量散佈光譜儀（EDX）等材料檢測方法來探討與建構鍺量子點在氮化矽中獨特的移動行為機制，如此就能精確地掌控量子點在氮化矽中的位置、大小與結晶形態。變溫與變強度光子激發光（PL）的量測結果證實在3.3 eV的放射峰值主要是來自於鍺量子點內部的自由激子傳輸 （free exciton transition），而且此放射峰值的波長會隨著量子點直徑的縮小而展現出藍移的現象。
藉由多次複晶矽鍺沉積與氧化製程的堆疊技術，得以形成量子點大小均勻或漸進改變的三維鍺量子點陣列，進而實際研製出高品質的可見光光二極體。同時我們也設計鍺量子點在氮化矽層中的位置，使鍺量子點掩埋於氮化矽層中或直接接觸到矽基板，分別製作出以感應電流或以激子穿隧電流為主要傳輸機制的高光響應度的光二極體。

關鍵字

多面形的鍺量子點 ； 鍺量子點 ； 感應電流 ； 氮化矽局部氧化效應 ； 夾心蛋糕的技術 ； Ostwald 熟化現象

並列摘要

In this thesis, we demonstrated the precise placement of Ge quantum dots (QDs) in Si3N4 and SiO2 matrices by selectively oxidizing poly-SiGe-on-SiO2 or -Si3N4. Thereby, we are able to modulate electronic structure of Ge QDs by means of altering their size and the host materials based on the quantum confinement effects. The QD size and crystallinity appear to be strongly influenced by the host materials.
Using the catalytically-enhanced local oxidation of Si3N4 by Ge QDs, we have successfully placed the Ge QDs into Si3N4 layer. We investigate the unique migration behavior of Ge QDs burrowing into the underneath Si3N4 by transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis, so that we can precisely control the position, size and the crystal morphology of Ge QDs embedded in Si3N4. The power dependent and temperature dependent photoluminescence (PL) spectra show that the peak centered at 3.3 eV is dominated by free exciton transition in the Ge QDs. The PL spectra reveal a blueshift in peak energy as the dot size decreases.
We have fabricated both uniform-sized or grading-sized Ge QDs array for high performance visible-light photo-diodes by repeating the stack deposition and oxidation of Si3N4/poly-SiGe/SiO2 in layer-cake technique. The significant photocurrent enhancement in Ge QD photodiodes is inferred from the photoexcited exciton tunneling or photoinduced conduction currents.

並列關鍵字

catalytically-enhanced local oxidation of Si3N4 ； germanium quantum dot ； faceted germanium quantum dot ； Ostwald ripening ； layer-cake technique ； induced current

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