跳到主要內容

臺灣博碩士論文加值系統

(3.229.137.68) 您好!臺灣時間:2021/07/25 16:37
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

我願授權國圖
: 
twitterline
研究生:梁建欽
研究生(外文):Jian-Chin Liang
論文名稱:氮化鎵材料之飛秒載子動力學研究
論文名稱(外文):Studies of Carrier Dynamics in GaN Based Materials
指導教授:孫啟光孫啟光引用關係
指導教授(外文):Chi-Kuang Sun
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:光電工程學研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2000
畢業學年度:88
語文別:英文
論文頁數:70
中文關鍵詞:超快光譜學氮化鎵激發探測法同調聲子帶尾能階氮化鎵銦/氮化鎵多重量子井結構千兆赫壓電場
外文關鍵詞:ultrafast spectroscopyGaNpump-probecoherent phononbandtailInGaN/GaN MQWsterahertzpizeoelectric field
相關次數:
  • 被引用被引用:0
  • 點閱點閱:219
  • 評分評分:
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
在本篇論文中,我們利用飛秒雷射的穿透式激發探測法,來研究非故意摻雜氮化鎵材料中帶尾能階的載子動力學。過去許多研究指出氮化鎵雷射主要的放光機制來自於帶尾能階發光,並把此帶尾能階視局限能階。然而,由我們的實驗結果顯示帶尾能階未必是局限能階。實驗所得之暫態響應顯示:較淺的帶尾能階是連續能階,只有較深的帶尾能階才是局限能階。在淺帶尾能階的載子完成外部熱平衡的時間與熱載子冷卻所需要的時間同樣在500飛秒以內。相對的,在深帶尾能階的載子行為,則由聲學聲子協助的穿遂所主導,使載子能移動到較低能量的能階。
我們也利用相同的方法來量測氮化鎵銦/氮化鎵多重量子井結構的樣品。巨大的同調聲學聲子振盪首次被量得,所引起的穿透量的調制可高達1%,是以往量得的聲子振盪所引起的反射率調制的103倍。不同於往量測的半導體材料,氮化鎵銦/氮化鎵多重量子井結構中存在著應力所引起的巨大壓電場;當紫外光的飛秒脈衝在樣品中產生載子時,這些載子會因壓電場而分離,並同時遮蔽部份的壓電場,並引發同調的縱向聲學聲子位移式的震盪,使我們得以在穿透式激發探測實驗中看到吸收的震盪。同調聲學聲子頻率是由呈週期性的載子分佈所決定,並不須考慮多重量子井結構造成的區域折疊模態;同時我們也可以調整多重量子井結構的週期來改變振盪頻率,使氮化鎵銦/氮化鎵多重量子井結構可應用於可調的千兆赫(1012 Hz)波段光電元件。利用量子局限的Franz-Keldysh效應可以成功解釋實驗中量到吸收的震盪大小和量測能量的關係,顯示所量測到之劇烈振盪是由於聲子震盪所產生之電場變化所引發。所量得的劇烈振盪在數個微微秒(10-12秒)內衰減,遠比聲子生命期短,顯然與以往的研究結果不同。在我們實驗中,是由於有限的樣品厚度,造成波前向量的不確定性,以致於同調震盪快速失去相位間的關係。

In this thesis, ultrafast carrier dynamics of bandtail states in an unintentionally doped GaN sample was investigated using femtosecond transmission pump-probe measurements. Many reports suggested that the laser emission in InGaN/GaN multiple-quantum-wells laser diode was considered to originate form the bandtail states. The bandtail states in GaN were always regarded as excitons localized at deep trap states. However, our studies indicate that not all bandtail states are localized states. The transient responses suggest that the shallow bandtail states are extended states and deep bandtail states are localized states. The carriers in shallow bandtail states are found to externally thermalize within 500 fs, at the same rate as the above bandgap carriers. The carriers in deep bandtail states are, on the other hand, dominated by carrier transfer into the lower energy states through phonon assisted tunneling.
InGaN/GaN multiple-quantum-wells with strong strain-induced piezoelectric fields was also investigated by femtosecond transmission pump-probe measurement in this thesis. Huge coherent acoustic phonon oscillation was observed for the first time and the induced optical transmission modulation on the order of 1% can be easily achieved. The optical property modulation is 103 times of the coherent-phonon-induced reflectivity modulation in pervious reports in other semiconductors. With UV femtosecond pulse excitation, photogenerated carriers screened the piezoelectric field in InGaN/GaN MWQs and initiated the displacive oscillations of the coherent longitudinal-acoustic phonon. The specific coherent phonon frequency was selected by the coupling between the periodic carrier distribution and the corresponding acoustic phonon mode. Thus InGaN/GaN multiple-quantum-wells can be applied to high-speed optoelectronic applications with a tunable oscillation frequency in THz region by tuning the period with of multiple-quantum-wells. The relation between the absorption oscillation and the probe photon energy can be explained through the quantum confined Franz-Keldysh effect, indicating that the huge oscillation was induced by modulation of piezoelectric field resulted from the phonon oscillation. The decay time observed in the transmission modulation on the order of several picoseconds is much shorter than the lifetime of coherent acoustic phonon, which was responsible for the decay time in previous reports. The uncertainty of carrier distribution wavevector due to the finite sample width was found to determine the observed fast dephasing time of the coherent oscillation.

Chapter 1. Introduction
1.1 GaN-based Semiconductor: Physics and Applications
1.2 Ultrafast Carrier Dynamics in Semiconductor
1.3 Femtosecond Pump-probe technique
1.4 Thesis Structure
Chapter 2. Experiments
2.1 Generation of Ultraviolet Femtosecond Pulse
2.2 Experimental setup of UV femtosecond pump-probe measurement
2.3 Sample preparation
A. Unintentionally doped GaN thin film
B. InGaN/GaN multiple-quantum-wells
Chapter 3. Carrier Dynamics in GaN Bandtail States
3.1 Bandtail States in GaN-based Semiconductor
3.2 Carrier Dynamics above Bandgap
3.3 Carrier Dynamics below Bandgap
A. Carrier Dynamics in Shallow Bandtail
B. Carrier Dynamics in Deep Bandtail
3.4 Mobility Edge Measurement
Chapter 4. Coherent Acoustic Phonon Oscillations in InGaN/GaN MQWs
4.1 Coherent Phonon Oscillations in Semiconductor
4.2 Coherent Acoustic Phonon Oscillations in InGaN/GaN MQWs
4.3 Fast Dephasing Time of Coherent Acoustic Phonon Oscillations in InGaN/GaN MQWs
Chapter 5. Summary

1.B. P. Keller, S. Keller, D. Kapolnek, W.-N Jiang, Y.-F. Wu, H. Masui, X, H. Wu, B. Heying, J. S. Speck, U. K. Mishra, and S. P. DenBaars, "Metalorganic Chemical vapor deposition growth of high optical quality and high mobility GaN", J. Electron. Mater, vol. 24, pp. 1707-1709 (1995).
2.S. Nakamura and G. Fasol, The Blue Laser Diode, Springer-Verlag Berlin Heidelberg (1997).
3.S.. Nakamura, M. Senoh, and S. Nagahama, "High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures", Jpn. J. Appl. Phys. part 2, vol. 34, pp. L797-L899 (1995).
4.S. Nakamura, M. Senoh, and S. Nagahama, "InGaN/GaN/AlGaN-Based Laser Diodes with Modulation-Doped Strained-Layer Superlattices", Jpn. J. Appl. Phys. part 2, vol. 36, pp. L1568-L1570 (1997).
5.S. Nakamura, M. Senoh, and S. Nagahama, "InGaN/GaN/AlGaN-based laser diodes with modulation-doped strained-layer superlattices grown on an epitaxially laterally overgrown GaN substrate", Appl. Phys. Lett., vol. 72, pp.211-223 (1998).
6.S. A. Lyon, "Spectroscopy of hot carriers in semiconductor", J. Luminescence, vol. 35, pp. 121-154 (1986).
7.A. Othonos, "Probing ultrafast carrier and phonon dynamics in semiconductors", Appl. Phys. Rev., vol. 4, pp. 1789-1830 (1998).
8.S. L. Shopiro, Ultrafast Light Pulses, Springer-Verlag, (1977).

QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top
無相關期刊