不同結構之氮化銦鎵/氮化鎵量子井結構發光二極體 之光學與材料特性研究

Optical Properties and Material Studies of Different InGaN/GaN Multi-Quantum Well Structures Light Emitting Diode Wafer

郭庭瑋(Ting-Wei Kuo)

指導教授 ： 馮哲川

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.2008.10259

摘要

本論文主要分析氮化銦鎵/氮化鎵多重量子井的光學與材料結構特性，透過穿透式電子顯微鏡實驗、X光繞射光、激螢光光譜以及光激螢光激發光譜及時間鑑別光激螢光頻譜，來研究其材料結構與光學特性。
在第一部份中，我們研究不同銦含量之量子井藍光及多磊晶了一組量子井藍光之氮化銦鎵/氮化鎵多重量子井樣品的光學及材料結構特性。由光激螢光光譜之溫度變化比較中，可以知道在光激螢光光譜中所觀察到的量子井相關訊號，並不完全是來自於能帶間躍遷的訊號，有一部分可能是來自於在氮化銦鎵量子井中銦組成的不均勻性，造成位能波動起伏所形成的侷限態的躍遷訊號。隨著溫度升高訊號有紅位移的趨勢並伴隨著半寬的增加，利用活化能的經驗公式模擬可以知道氮化銦鎵/氮化鎵多重量子井的活化能約數十毫到數百毫電子伏特。當氮化銦鎵/氮化鎵多重量子井之銦含量增加，活化能增加以及再多增加一組量子井，因缺陷密度及載子侷限效果也會跟著增加，活化能增加。然後利用時間鑑別光激發光頻譜，當氮化銦鎵/氮化鎵多重量子井之銦含量增加，衰退時間較大。然後透過光激螢光激發實驗，我們觀察到很大的史托克位移，這主要是由於銦濃度變化與量子侷限史塔克效應的影響。最後由X 光繞射及穿透式電子顯微鏡實驗，我們可以測定樣品的量子井厚度以及量子井中的銦含量。
在第二部份中，我們研究不同量子井的成長溫度不同的氮化銦鎵/氮化鎵多重量子井樣品及另一個不同量子井結構樣品的光學及材料結構特性。當氮化銦鎵/氮化鎵多重量子井之量子井磊晶溫度較低時，造成銦在沉積時比較好，因而銦含量增加了，整個光激螢光光譜紅移了，但因量子井磊晶溫度較低的關係造成樣品不均勻性與樣品品質不好。
由光激螢光光譜的溫度變化，我們發現氮化銦鎵量子井相關訊號存在著一個不尋常的發光現象。隨著溫度的升高，其峰值能量的改變呈現著一個S型的能量變化。利用能帶尾端侷限態之模型，即導電帶與價電帶尾端之狀態密度以高斯分佈來描述分析之。在時間鑑別光激發光頻譜中，因氮化銦鎵/氮化鎵多重量子井之銦含量增加，衰退時間較大。而在光激螢光激發實驗，我們觀察到有較大的史托克位移，這主要是由於量子侷限史塔克效應的影響。在另一個不同結構的氮化銦鎵/氮化鎵多重量子井，不同結構所造成的光學特性。由X 光繞射及穿透式電子顯微鏡實驗，我們可以測定樣品的量子井厚度以及量子井中的銦含量。另外我們可以觀察另一個不同結構所造成的光學特性.

關鍵字

氮化銦鎵/氮化鎵量子井結構發光二極體 ； 光激螢光激發光譜 ； 激螢光光譜 ； 間鑑別光激螢光頻譜

並列摘要

This thesis concerns with the studies on the optical properties and material characteristics of InGaN/GaN multi-quantum wells LED structure. By the X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), photoluminescence excitation (PLE), time-resolved photoluminescence (TRPL), experiments were carried out to study the optical and material structure properties.
(1) InGaN/GaN LEDs with different QW number structures and different Indium compositions:
First, we studied the optical and material structure properties of the blue emission MQW LED samples with different indium composition and different QW number. The temperature dependent PL shows that the signal from InGaN QWs was influenced by two kinds of matters. One is the band to band transition of InGaN; the other is the localization effect cause by the non-uniformity of the In composition in In-rich samples. While the temperature increasing, full width half maximum increases, and the signal tends to the red shift. By using the fitting formula of activation energy, the activation energies (Ea) of the InGaN MQW samples were obtained. A Time-resolved photoluminescence is invested in InGaN/GaN multiple quantum wells, while the indium composition increasing and QW number increasing, and a longer decay time. From the results of PLE experiment, a large Stokes shift (SS) was observed. The large Stokes shift can be attributed to the variation in indium composition or the quantum confined Stark effect (QCSE).
And the Photoluminescence spectra exhibit weak blue peaks and we showed that the optical intensity is improved by the number of wells. Finally, from the XRD and TEM experimental results, we can determine the period thickness and indium composition of the sample.
(2) Dual wavelength InGaN/GaN multi-quantum well LEDs:
Second, we studied the optical and material structure properties of dual wavelength MQW LED samples with different well growth-temperature and different dual wavelength MQWs LED structure. Here, we repute the dual wavelength InGaN/GaN MQWs structure LEDs is modifiable charge asymmetric resonance tunneling structure (CART InGaN/GaN MQWs LEDs). We have studied two InGaN MQWs samples with different well growing temperature, and also explored the influence of growth temperature of the well on the structural and optical properties. The PL spectrums show that the emission wavelength shift toward the side of long wavelength (red shifts) due to lower growth temperature. The deposition (composition) of Indium is better (higher) than the higher growth temperature, and furthermore the activation energy (localization depth) is relatively higher (deeper). Another, we can change MQWs to get the emission wavelength that we want. We discuss different CART InGaN/GaN MQW structure. We can observe theirs optical characteristic.

並列關鍵字

InGaN/GaN ； MQW ； TRPL ； PL,PLE ； CART-QW,

參考文獻

[1.3] Koga K and Yamaguchi T, Prog. Crystal Growth Character 23, 127 (1991).

[1.5] S. Nakamura et al., The Blue Laser Diodes (Spring, 1997), Chap.2.

[1.9] S. Nakamura, Jpn. J. Appl. Phys. 30, L1705 (1991).

[1.10] F. Bertram, T. Riemann, J. Christen, A. Kaschner, A. Hoffmann, C. Thomsen, K. Hiramatsu, T. Shibata and N. Sawaki, “Strain relaxation and strong impurity incorporation in epitaxial laterally overgrown GaN: Direct imaging of different growth domains by cathodoluminescence microscopy and micro-Raman spectroscopy,” Appl. Phys. Lett. 74, 359 (1999).

[1.11] S. Nakamura, M. Senoh, S Nagahama, N. Iwasa, T. Yamada, T. Matsushita, H. Kiyoku, Y. Sugimoto, T. Kozaki, H. Umemoto, M. Sano, and K. Chocho, “Continuous-wave operation of InGaN/GaN/AlGaN-based laser diodes grown on GaN substrates,” Appl. Phys. Lett.72, 2014 (1998).