标题: 不同载子密度下串联量子尖端接触的电性传输
carrier density influenced electrical transport of double quantum point contacts in series
作者: 林欣毅
Lin, Hsin-I
许世英
Hsu, Shih-Ying
电子物理系所
关键字: 二维电子气;量子尖端接触;2DEG;quantum point contact
公开日期: 2008
摘要: 本论文是研究低温时在不同载子密度下串联量子尖端接触的电性传输。我们利用微影制程技术在高迁移率的GaAs/AlGaAs异质结构上制作多对串联型式的金属闸极,并在串联传输通道上方隔着绝缘层制作控制电极,藉此控制下层传输通道内的载子密度并观察其电性传输。
在数据分析上,我们利用Beenakker的理论模型分析串联通道下的电性传输情形,直接穿透率系数Td可以描绘电子从某通道穿越至另一通道的弹道式传输比例多寡,并藉此分析电性传输的特性。实验结果显示Td随着控制闸极电压下降而下降,载子传输在高载子密度区展现部分的绝热传输,但在低载子密度区却呈现完全的欧姆传输,我们把它归因于低载子密度下平均自由径与同调长度的减少。
We have studied the ballistic electron transport of double quantum point contacts(QPCs) in series with different carrier densities at low temperatures. Our sample is fabricated by the lithographic technology on a high mobility GaAs/AlGaAs heterostructure. In this device, two pairs of metal gate are placed longitudinally and sequentially with an edge-to-edge distance of 600nm. Isolating from an insulating layer, a top gate is also fabricated on the top of the quantum wires to modify the carrier density in the quantum wires and the two dimensional electron gas as well.
In our analysis, we used Beenakker model to understand the electric transport behaviors. The electric transport is characterized by the direct transmission coefficient Td which represents the portions of electrons traveling ballistically from one quantum wire to the other. Our results show that the parameter Td decreases with decreasing carrier density. The transport is partially adiabatic in high electron densities and transits to completely ohmic regimes in low densities. Because of the correlation between the coherence length and transmission coefficient, we attribute the result to the reduction of the mean free path and the coherence of electron.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079621535
http://hdl.handle.net/11536/42450
显示于类别:Thesis


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