Study On Electron Spin-polarization Characterization In Two-dimension Electron Gas Modulated By Magnetic And Electron Fields

It is based on the electron’s charge and its degrees of freedom for traditional electronics and information technology.With the development of spintronics,inspiring researchers’ interest,the degrees of freedom of both spin and charge of electrons will induce many new and exotic spin-dominated transport and make them promising for new types of logic devices.It is regarded as the ultimate goal for practical application at high processing speed,low power consumption,and non-volatile memory storage capabilities.The new type of devices should be easier to compatible with the traditional electronics devices.Although it is easier to modulate the spin of electrons in the metallic material,it is difficult to integrate the metallic material with the traditional semiconductor material.Because the resistance is different between the metallic and semiconductor material,the difference is much bigger at the interface between the metallic and semiconductor materials.Therefore,the efficiency of electron injection is especially lower.Meanwhile,it is also difficult to grow high quantality semiconductor material on the surface of metallic material.In order to solve this question,the finding that modulating the electron in two-dimension gas by using the ferromagnetic stripe and Schottky normal-metal stripe is useful,which can provide an effective approach to modulating the spin of electrons.In this paper,the electronical transport has been deeply investigated in double delta magnetically nanostructure.Meanwhile,it has been studied how to create the basic magnetic nanostructure and describe this model into mathematical language by an equation.Furthermore,for numerical convenience,a method that all the relevant quantities written in dimensionless in the equation have been introduced.Therefore,according to the resolution of this equation and the boundary condition of this model,a transfer matrix has been gotten,in which three quantities,the incident amplitude,the reflection amplitude r,and the transmission amplitude have appeared.So,it is easy to get the transmission coefficient through the matrix.Based on reading a lot of published papers and recalculating some results,the studying in this paper is divided into three parts.Firstly,the influence of the angle between double delta magnetic barriers on electron transport has been investigated.The parallel and anti-parallel magnetically nanostructure have been studied by some researchers,but,it’s a little bit difficult to fabricate absolutely parallel or antiparallel double magnetic barriers.Thus,in order to lower the demand for high precision,the investigation on the influence of the angle changing between magnetic fields on electron transport becomes more essential.A method by using the Goos-H(?)nchen shift and the spin polarization has been adopted to analyze the influence of the angle on electron transport in In As systems.The result has shown that a stable spin polarization can be obtained under some special structural parameters.Secondly,the influence of the bias on the spin electron transport has been considered.The method of using the bias to modulate the spin electron transport is one of the great efficient methods,which can be realized by a transverse magnetic field.The bias modulation is similar to the strain modulation,which can be simplified into a triangular barrier model to modulate.The difference which the term of bias should be adopted positive sign or negative sign in the equation has been founded in some published papers.Therefore,this question has been analyzed carefully in chapter Ⅱ and the equation has been transferred into dimensionless type.Furthermore,due to the action of bias in the model,the linear first-order term has appeared in the equation.For simplicity,the Airy function has been used as the resolution of the function,which not only decreases the process of calculation by using several square barriers replacing the triangle barrier but also increases the accuracy of the results.All these theories have been applied to study the influence of bias on spin electron transport by calculating the Goos-H(?)nchen shift and the spin polarization modulated in In As system.The results compared with some published results have shown spin polarization existing much stronger variation,when modulating the structural parameter is close to its critical value and Its boundary character is more sensitive.Thirdly,the influence of the finite periodic magnetic barriers superlattices on the spin electron transport has been investigated.In the processing of reading and calculating some published papers,it has been found that although some nanostructures are period in physical structure,if its potential constructed structure is not available,the same results with paper cannot be repeated.Therefore,according to these studies,two basic rules can be used to judge whether the nanostructure is period or not.One is the physical structure is period,the other is the potential structure is also period.If a nanostructure follows the rules,it will be a finite periodic barriers/wells superlattices.Meanwhile,the relation between the transmission probability for n identical periodic structure and the transmission probability for unit structure has been studied in this paper,which is very useful to decrease the processing of calculation and increase the accuracy of the calculation.These theories have been used to investigate the influence of n periodic superlattices on spin electron transport by calculating transmission coefficient,conductance,and spin polarization in In As system.The results show the resonant peak can be induced by splitting into(n-1)fold with n units structure for the transmission probability,the conductance,and the spin polarization.To sum up,all methods studied in this paper can not only be used to analyze the spin electron transport in In As system but also to analyze the spin electron transport in other materials systems.Meanwhile,it is quite meaningful for using these results to design some semiconductor filters,and multichannel nanostructure electron wave filters and to work as a reference in fabricating these filters.