矽量子點單電子電晶體之電子傳輸

中文摘要使用先進的電子束曝光技術搭配光學微影半導體製程技術，在絕緣層上矽晶片上製作矽奈米結構，再利用乾式熱氧化進一步將結構線寬縮小並形成單電子電晶體元件，並在低溫環境下研究其電子傳輸特性。首先，研究一大尺寸量子點串聯一小尺寸量子點所組成的單電子電晶體元件，在直流導電特性量測中，大尺寸量子點所造成的小週期庫倫震盪會依附在由小尺寸量子點所造成之大的非週期性庫倫震盪上，而後者的電流震盪波峰在外加磁場條件下會產生偏移，這個現象是由於磁場對量子點(侷限位能井)內的能階產生Landau偏移效應，另外在超過臨界磁場後庫倫電流波峰會消失，這是由於傳導電子在量子點內進行迴旋運動所造成之侷限現象。接續的研究是由非常短的矽奈米細線所形成之雙耦合量子點單電子電晶體。在2K低溫下，電流在低偏壓範圍內明顯地被充電效應所抑制，而當偏壓大過庫倫阻斷區域後，電流對電壓曲線會出現數個電流峰，這現象由於兩個量子點內的能階於相互精確對準時，才會有最大的穿隧效率，若偏離此對準點則穿隧電流會迅速下降，超過對準點(即電流波峰處)電壓後，雖然增加電壓而電流卻反而下降，即所謂的[負微分電阻現象]。上述的共振穿隧電流會隨著外加磁場強度增加而變大，我們以數值模擬的方法來說明與驗證上述觀察到的現象。

關鍵字

矽,單電子電晶體,耦合量子點,絕緣層上矽,共振穿隧現象,電子束微影技術

並列摘要

Abstract First, we have fabricated and measured a lateral Si single electron transistor consisting of a succession of a big island and small quantum dots. The big island gives rise to a small period Coulomb oscillation riding on the large irregular oscillation arising from the small quantum dots. The peaks of the latter shift in the presence of a magnetic field, which is analyzed in the context of field-induced Landau level shift with a soft-wall confinement potential. Furthermore, the current peak was suppressed for fields beyond a threshold value. An explanation based on cyclotron localization at noninteracting Landau levels is presented. Next, we report fabrication, measurement and simulation of silicon single-electron- transistors made on silicon-on-insulator wafers. At T~2K, these devices showed clear Coulomb blockade structures. External perpendicular magnetic field was found to enhance the resonant tunneling peak and was used to ascertain the presence of two laterally coupled quantum dots in the narrow constriction between the source-drain electrodes. The proposed model and measured experimental data were consistently explained using numerical simulations.

並列關鍵字

silicon,single electron transistor,quantum dot,resonant tunneling,electron beam lithography

參考文獻

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矽量子點單電子電晶體之電子傳輸

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