Wave Vector Filtering Effect And Manipulation For Electrons In Magnetically And Electrically Confined Semiconductor Heterostructure

By using modern materials growth techniques,it is possible to realize the so-called magnetically modulated semiconductor nanostructure in experiments,which is a kind of hybrid quantum small systems consisting of magnetic materials and semiconductors.Due to small size,low dimension,and quantum confinement,a magnetically modulated semiconductor nanostructure possesses abundant of quantum effects,such as spin polarization effect,giant magnetoresistance effect,etc.Moreover,these novel effects can be employed to design and develop new nanoelectronics devices,e.g.,electron-momentum filter and spatial spin splitter.In recent years,quantum effect,manipulation and device application in magnetically modulated semiconductor nanostructures have become a significant research direction in condensed matter physics,materials science,semiconductor physics and device,and so on.Adopting theoretical analysis combining with numerical calculation,this thesis explores wave vector filtering(WVF)effect and its manipulation for electrons in an important class of magnetically modulated semiconductors nanostructure---magnetically and electrically confined semiconductor heterostructure(MECSH),focusing on developing new controllable electron-momentum filter for nanoelectronics device applications.This thesis is divided into six chapters.The first chapter briefly introduces magnetically modulated semiconductor nanostructure,research progress of wave filtering effect and research content of this thesis.In chapter two,we introduce theory and method exploited in thesis,including improved transfer-matrix method and numerical differential method.The third chapter investigates WVF effect for electrons in the MECSH.In chapter 4,we study influence of Delta-doping on WVF effect for electrons across the MECSH device.The fifth chapter discusses modulation of traverse electric field or applied bias to WVF effect when electrons tunnel through the MECSH device.In final chapter,we summarize research results obtained in whole thesis,point out deficiencies existing in thesis research,and look forward to research direction in the future.Research results obtained in this thesis mainly include four aspects as follows:(1)A considerable WVF effect is found to appear in considered MECSH,since electronic transmission through a magnetically modulated semiconductor nanostructure depends on its longitudinal wave vector---an essentially two-dimensional(2D)process.Furthermore,its WVF efficiency is associated with width,position and applied voltage of the SM stripe in the MECSH,the optimal electron WVF effect can be achieved,therefore,by properly fabricating SM stripe,which can be explained from the dependence of effective potential felt by electronsin the MECSH on SM-stripe parameters.(2)After a Delta-doping is embedded inside,an obvious WVF effect still exists in considered MECSH device,which is because the Delta-doping does not change the fact---an essentially 2D process for electrons across a magnetically modulated semiconductor nanostructure.However,such a Delta-doping will impact greatly on electron WVF effect,namely,the degree of WVF effect can be controlled by changing weight or position of the Delta-doping.This attributes to the dependence of the effective potential experienced by electrons in the MECSH on the Delta-doping,which will give rise to a correlation of electronic transmission to weight or position of the Delta-doping.(3)When applying a bias to the MECSH device---a traverse electric field appears along electronic transport direction,an evident WVF effect still exists for electrons in the MECSH device,which can be understood because applied bias or external electric field does not change the characteristic of the essentially 2D process for electrons to traverse the MECSH.However,the effective potential for electrons in the MECSH device is related to applied bias or external electric field,the WVF efficiency can be,therefore,manipulated by switching strength or direction of the applied electric field.(4)Our studied MECSH can be used as a new controllable electron-momentum filter for nanoelectronics device applications,whose WVF efficiency can be effectively tuned by SM stripe in system,Delta-doping,and applied bias or traverse electric field.Therefore,these research results obtained in the thesis not only can provide a reference for quantum manipulating in semiconductor nanostructures,but also can put forward a new type of electron-momentum filter device.