砷化銦/砷化鎵量子點耦合多層結構之光學特性分析

Optical properties of vertical coupling InAs/GaAs multilayer quantum dots

游尚衡(Shang-Heng Yu)

指導教授 ： 王智祥

中原大學/理學院/應用物理研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600277

摘要

本文探討不同長晶條件下成長的砷化銦/砷化鎵量子點耦合多層結構之光學特性。 A系列樣品是以低成長速率(0.029 ML/s)成長，並選擇量子點層數(N)為三十層，不同砷化鎵夾層厚度砷化銦/砷化鎵量子點耦合多層結構。 B系列樣品是以較高的成長速率(0.088 ML/s)成長，並選擇砷化鎵夾層厚度為17nm的砷化銦/砷化鎵量子點耦合多層結構，改變量子點層數(N)從單層到三十層。
對A系列樣品而言，從光激螢光實驗中，發現隨著夾層厚度的縮減，量子點裡的銦元素與夾層裡的鎵元素會因為擴散作用，而造成能量藍位移的現象，而擴散作用是因為隨著夾層厚度的減小，強烈的應變耦合而產生，而此擴散作用也會隨著長晶的方向，越來越劇烈，以上現象從經過化學蝕刻過的樣品其光激螢光實驗中得到證實，而上述實驗也可以區別出不同深度的量子點結構其光學特性，特別是接近表面的量子點與底層的量子點。
對B系列樣品而言，藉由較高的長晶速率，因擴散作用而造成的能量藍位移現象被成功的抑制，從光激螢光光譜中，發現從單層結構到三十層多層結構，會有因為共振式電子穿襚機制而造成的能量紅位移現象。 但是對於三十層的結構而言，因為隨著層數增加而持續增加的的應變場，還是會造成擴散作用現象，這成功的說明了為什麼從十層結構到三十層結構，只有大約8 meV 的能量紅位移，而其實電子共振式穿襚現象還是主導了最後光激螢光訊號的位移趨勢。 另外我們還藉由共振式電子穿襚現象，成功的調制B系列樣品其光激螢光發光波長在室溫下達到1.3μm波段，對於光纖通訊產業的元件製備，B系列樣品是不錯的選擇。

關鍵字

光激螢光 ； 量子點 ； 砷化銦/砷化鎵 ； 垂直耦合

並列摘要

We investigate the optical properties of electronic vertical coupling InAs/GaAs multilayer QDs with different growth condition. A-series samples are InAs/GaAs 30 layers QDs structures with different GaAs spacer thickness from 30 nm to 10 nm, the QDs growth rate is 0.029 ML/s. B-series samples are InAs/GaAs multilayer QDs structures with 17 nm GaAs spacer thickness and change multilayer numbers (N) from N=1 to N=30, the QDs growth rate is 0.088 ML/s.
For A-series samples, in photoluminescence (PL) measurements, a significant energy blue-shift with decreasing spacer thickness due to inter-diffusion of In in QDs layer and Ga in spacer was observed. The inter-diffusion is caused by large strain-field coupling with decreasing spacer thickness, and will be enhanced with increasing multilayer numbers, too. It was confirmed by PL measurements of A and B series multilayer samples with applying chemical etching process to gradually remove the upper QDs layers. By this method the identification of the optical properties of upper QDs layers and down QDs layers was done.
For B-series samples, the energy blue-shift due to inter-diffusion is significantly suppressed by using a higher growth rate (0.088 ML/s) for QDs growth. In PL experiments, with increasing multilayer numbers from N=1 to N=30, the energy red-shift due to electronic resonant tunneling is observed. But for sampleB3 (N=30), the inter-diffusion still exist which can not completely eliminate due to continuously increasing strain with increasing multilayer numbers, and causes only a slight energy red-shift about 8 meV from sampleB2 (N=10) to sampleB3 (N=30). However, the mini-band formation due to the super-lattice structures still dominated the energy red-shift tendency. Finally, we successfully achieve PL emission wavelength to 1.3 μm at room temperature by InAs/GaAs QDs super-lattice structures. For device fabrication designing in optical communication industry, the B-series samples are excellent candidates.

並列關鍵字

multilayer quantum dots ； Photoluminescence ； vertical coupling ； InAs/GaAs

參考文獻

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