半導體異質結構中電子自旋相依傳輸

Abstract

我們提出了半導體二維通道中電子自旋相依傳輸的理論研究，考慮兩種不同的散射源：量子點（反量子點）以及分佈在半導體二維通道內或是周圍受到屏蔽的雜質，我們的研究主要是採用有效的單電子能帶Hamiltonian以及Rashba自旋軌域作用的理論，由於要處理二維通道中電子散射的問題，我們參照一般的方法將此三維的有效單電子能帶Hamiltonian做一個平均，沿著長晶方向（z方向）平均以後，我們即處理一個似(quasi)二維薛丁格方程式，利用部份波(partial-waves)以及變異相位的方法(variable phase approach)來數值解此一問題。 我們計算了極化朝z方向的電子之莫特散射截面(Mott scattering cross section)和雪曼函數(Sherman function)，發現了被InAs/GaAs量子點（反量子點）以及CdTe/InSb/CdTe、AlInAs/InGaAs/AlInAs對稱量子井中的雜質所散射的電子，在彈性截面上有很大的自旋相依不對稱，我們估計兩種不同散射源的雪曼函數大小可以達到0.01，此外基於波滋曼傳輸方程式，我們估算由自旋軌域作用所造成的不規則的霍爾效應(anomalous Hall effect)，系統在無外加磁場下，計算了導電率的矩陣元素並得到了可量測大約等於 的不規則霍爾角度(anomalous Hall angle)。

We present a theoretical study of the spin-dependent electron scattering from two types of scatterers: quantum dots(anti-dots) and screened impurities located at or near two-dimensional channels of III-V semiconductors. Our investigation is based on the effective one band Hamiltonian and the Rashba spin-orbit interaction. Because of our dealing with electrons scattering in two-dimensional channels, the three dimensional Hamiltonian is averaged following the general procedure. After the averaging along the structure growth direction (z-axis), we solve the quasi two-dimensional equation. The methods of partial waves and variable phase approach are used and the problems are solved numerically. We calculated the Mott scattering cross section and the Sherman function for electrons polarized along z-direction. We have found a large spin-dependent asymmetry in the elastic cross section for electrons scattered from InAs/GaAs quantum dots(anti-dots) and impurities in CdTe/InSb/CdTe and AlInAs/InGaAs/AlInAs symmetrical quantum wells. The Sherman function amplitude was predicted to reach about 0.01 for two types of scatterers. Based on the Boltzmann transport equation, we estimated the anomalous Hall effect due to the spin-orbit interaction. The elements of the conductivity matrices were calculated and we obtained a measurable anomalous Hall angle about at zero magnetic field in our system.