四族元素光躍遷機制之強化

Enhancement of Optical Transitions in Group IV Element

彭國倫(Kuo-Lun Peng)

指導教授 ： 劉致為

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10321

摘要

本論文中，我們藉由兩種不同的激發方式:光激發光和電激發光，觀察到鍺的直接能隙和非直接能隙的放光現象，同時我們探討兩者之間競爭性的發光復合機制。
在溫度升高的情況下，直接能隙的放光強度其增益大於非直接能隙的放光強度增益。此增益現象的主要原因有二：兩者的能隙差值縮小和因溫度提高而使得在費米分佈中高能量的載子數目有所增加。高濃度磣雜的鍺、提高光激發光使用的雷射能量和增加電激發光中的注入電流亦可使電子的費米能階往高能量移動並使得直接能隙的放光有所增加。無論是直接能隙或非直接能隙都可藉由物理模型去加以模擬並解釋。
外加雙軸張應力可減少直接能隙與非直接能隙的能帶差，累積更多的電子在直接能隙並產生增強放光的現象。藉由物理模型得到的能帶值和藉由理論計算出的能帶值兩者相當吻合。

關鍵字

鍺 ； 直接能隙 ； 光激發光 ； 電激發光 ； 張應力

並列摘要

In this thesis, both direct and indirect transitions of photoluminescence and electroluminescence are observed in Ge and the competitive radiative recombination between direct and indirect transition s are discussed.
The relative intensity of direct radiative recombination with respect to indirect radiative recombination increases with high temperature. The reduction in band gap and more carriers move toward in high energy region of Fermi-Dirac distribution are responsible for the enhancement. High doping concentration, increasing the optical pumping power and injection current moves the electron Fermi level upwards and the increase in electron population in direct valley enhance the luminescence. Each spectrum can be fitted by the sum of direct and indirect transition models.
The reduction in band gap difference between the L and Γ valleys by biaxial tensile strain increases the electron population in the direct valley and leads to strong enhancement. The band gap reduction in the direct and indirect valleys can be extracted from the photoluminescence spectra and is consistent with the calculations using K．P and deformation potential methods for valence bands and conduction bands, respectively.

並列關鍵字

germanium ； direct band gap ； photoluminescence ； electroluminescence ； tensile strain

參考文獻

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