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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/17549

Title: 兆赫幅射頻譜技術在薄膜系統之研究
Probing the Thin Film via Terahertz Spectroscopic Technique
Authors: Sheng-Hsien Hsu
許聖賢
Contributors: NTOU:Institute of Optoelectronic Sciences
國立臺灣海洋大學:光電科學研究所
Keywords: 兆赫幅射頻譜;兆赫幅射;薄膜
Terahertz;THz;thin film
Date: 2004
Issue Date: 2011-07-04
Abstract: 本論文利用THz頻譜技術研究氮化鎵(GaN)與氮化銦鎵(InGaN/GaN)多重量子井LED在THz波段的光學常數。我們建立一薄膜分析模型,經由此模型得到薄膜在THz波段的光學常數。這模型是利用穿越薄膜與基板的THz輻射電場(Et)與只穿過基板的THz輻射電場(Eref)的比值,並考慮THz輻射在薄膜內多重反射的效應,利用泰勒展開式簡化方程式,我們保留到二次項,以得到更精準的值。 對於GaN薄膜樣品在0.1到1.0 THz的折射率分佈於10.0到4.4,在1.0到2.0 THz的折射率分佈於4.4到2.8,在2.0到3.0 THz的折射率分佈於2.8到2.6,其0.1到3.0THz的吸收係數分佈於62mm-1到230mm-1。利用Drude model去fitting結果,我們可以得到GaN薄膜的載子濃度為3.7×10^17/cm3。比較此結果和霍爾效應量測的結果(1.47×10^18/cm3),我們發現霍爾效應測得的結果較大,原因是霍爾效應所量測到的是摻雜Si的N型GaN層的載子濃度,而THz頻譜技術量測到的載子濃度是緩衝層(butter layer)和未摻雜的GaN和摻雜Si的N型GaN的平均值。由實驗結果,可得到GaN的導電率在0.1到3.0THz分佈於19.2/Ωcm到13.4/Ωcm,其電漿頻率(plasma frequency)為11.64THz,載子碰撞率(carrier damping rate)為3.92THz。對於InGaN/GaN多重量子井LED在0.1到1.0THz的折射率分佈於11到4.6,在1.0到2.0 THz的折射率分佈於4.6到3.0,在2.0到3.0 THz的折射率分佈於3.0到2.9,其0.1到3.0THz的吸收係數分佈於65mm-1到252mm-1。同樣的,利用Drude model去fitting結果,我們可以得到InGaN/GaN多重量子井LED的載子濃度為3.5×10^17/cm3 以及導電率(0.1到3.0THz的導電率分佈於23.2/Ωcm到12.4/Ωcm),其電漿頻率(plasma frequency)為11.31THz,載子碰撞率(carrier damping rate)為3.08THz。
We have determined the complex conductivity and the refractive indices of GaN and InGaN/GaN MQWs LED by terahertz time-domain spectroscopy. Frequency dependent electron dynamics, power absorption and dispersion are obtained over the frequency range from 0.1 to 3.0THz. The index of refraction of the GaN film varies from 10.0 to 2.6. The power absorption of the GaN film varies from 62mm-1 to 230mm-1.The real conductivity of the GaN film varies from 19.2/Ωcm to 13.4/Ωcm. The transmission measurements of the GaN film are fit by simple Drude model. We obtain the plasma frequency and the carrier damping rate of the GaN film are 11.64THz and 3.92THz, respectively. The index of refraction of the InGaN/GaN MQWs LED varies from 11.0 to 2.9. The power absorption of the InGaN/GaN MQWs LED varies from 65mm-1 to 252mm-1. The real conductivity of the InGaN/GaN MQWs LED varies from 23.2/Ωcm to 12.4/Ωcm. The transmission measurements of the InGaN/GaN MQWs LED are fit by simple Drude model. We obtain the plasma frequency and the carrier damping rate of the InGaN/GaN MQWs LED are 11.31THz and 3.08THz, respectively.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M92880009
http://ntour.ntou.edu.tw/ir/handle/987654321/17549
Appears in Collections:[光電科學研究所] 博碩士論文

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