Wave Vector Filtering Effect And Its Manipulation For Electrons In Magnetically Modulated Semiconductor Nanostructures

Using advanced materials preparation technology,nanosized magnetic materials can be patterned on the surface of semiconductor heterostructure,create inhomogeneous magnetic fields,and confine high-mobility two-dimensional electron gas embedded in the interface of semiconductor heterostructure,which allows experimental researchers to construct magnetically modulated semiconductor nanostructure(MMSN).Due to small size,low dimensionality and quantum confinement,there are many novel quantum effects in MMSNs,and they can be used to design new nanoelectronic devices.Therefore,quantum effects and their manipulation in MMSNs have become a hot spot in the research field of nanoelectronics.Taking antiparallel asymmetric double δ-magnetic-barriers(AADDMB)and hybrid δ-magnetic-barrier and rectangular electric-barrier(HMBREB)as examples,this thesis investigates wave-vector filtering(WVF)effet and its control for electrons in MMSNs,with the aim of designing new manipulable electron-momentum filters.The whole thesis is divided into five chapters.Chapter 1 introduces MMSN,the research progress of WVF effect for electrons in MMSNs,and the research content of this thesis.In Chapter 2,we present theory and method exploited in this thesis,including the improved transfer-matrix method and the numerical differentiation.Chapter 3 investigates the WVF effect and the influence of δ-doping and applied bais voltage on it for electrons in AADDMB.In chapter 4,we put forward a new MMSN,hybrid δ-magnetic-barrier and rectangular electric-barrier(HMBREB)and study its WVF effect as well as control of δ-doping and applied bais to WVF effect.Finally,Chapter 5 summarises this thesis and outlook for follw-up researchs.The main results obtained in this thesis are as follows:(1)The effective potential experienced by electrons in a MMSN depends on its traverse wave vector,the process of electrons tunneling through a MMSN is,therefore,essentially two-dimensional.It is confirmed by researchs done in the thesis that a distinct WVF effect does exist for electron in MMSNs.Moreover,the WVF efficiency is closely related to structural parameters of a MMSN,a good WVF effect can be achieved by finely designing and fabricating the MMSN.(2)With the help of atomic-layer doping technology,a δ-doping is experimentally introduced into MMSNs.It is demonstrated that a considerable WVF effect still appears in δ-doped MMSNs,because the δ-doping does not eliminate the two-dimensional characteristic of electrons tunneling through a MMSN.However,the effective potential felt by electrons in MMSN is associated with the δ-doping.Therefore,changing weight or position of δ-doping can effectively manipulate WVF efficiency well,which maybe give rise as structurally-controllable electron-momentum filter.(3)Applying a bias voltage at the two ends of a MMSN,a tranverse electric field is generated along transport direction of electrons.However,this bias or electric field also does not annihilate the feature of two-dimensional process for electrons to traverse a MMSN,therefore,the WVF effect still exists in biased MMSNs.Besides,the WVF efficiency is handily modulated by changing magnitude or polarity of bias or electric field and electrically-tunable electron-momentum filter is obtained.To sum up,this thesis reveals the general law of the WVF effect for electrons in MMSNs and investigates the control of the WVF effect via the δ-doping or an applied bias.The obtained results not only have reference value for the quantum manipulation of semiconductor nanostructures,but also propose a new controllable electron-momentum filter for nanoelectronics.