InAs量子點蕭基二極體之導納頻譜分析與模擬

Abstract

本論文針對InAs量子點蕭基二極體的導納頻譜作探討，首先從實驗結果討論電導與電容在加大逆向偏壓、低頻(104~106赫茲)之下互相對應的差異之處，並在接下來的導納模擬當中提出兩個模型來驗證是否為量子點內的載子躍遷造成實驗中的結果。第一種假設考慮蕭基二極體中含有缺陷，在外加小訊號下，被費米能階調變到的缺陷會捕捉/放射電子而貢獻成電流；第二種模型考慮存在蕭基二極體中的量子點，其中被侷限的電子會因為被費米能階調變而被掃出空乏區。藉由以上模型的理論計算後，比較上述兩種模型的導納模擬圖，發現量子點的導納模擬會導致電容的反曲點與電導的峰值出現差異，並且量子點模型的電導圖型會呈現不對稱的現象，以此與實驗上的結果互相對照。

In this work, we focus on the frequency- resolved admittance spectroscopy of InAs/InGaAs dot-in-well layer embedded in a GaAs Schottky diode where the reverse bias is used to discharge the initially occupied energy levels. In the first part, the empirical results show the differences between capacitance versus frequency logarithm, and conductance versus frequency logarithm. To understand the cause of the correspondence between C and G influenced by quantum dots under large reverse bias and low frequency, we demonstrate an analytical expression for admittance. Consider two models: the first one, Schottky diode with defects; the second one contains quantum dots layer within. Derive the admittance of both cases by solving the electrical field and potential energy of the depletion region under small signal. Furthermore, analyze the simulated admittance spectroscopy of both models to verify the contribution of quantum dots.