Investigation Of The Electron Spin Diffusion Dynamics In A (110)-GaAs Quantum Well

Semiconductor spintronics expects to use an intrinsic property such as electron spin to replace the charge to achieve more powerful new semiconductor devices.Spintronics devices have the potential advantages of nonvolatility,increased data processing speed,decreased electric power consumption,and increased integration densities compared with conventional semiconductor devices.It draws increasing attention.To successfully realize spintronics devices,it is essential to effectively control injection,storage,manipulation,transport and detection of spin polarization in solid state systems.Some parameters such as long enough spin relaxation time and large enough spin diffusion length must be achieved.The study of spin diffusion properties in semiconductors has become a hot topic in the field of condensed matter physics.For the dynamics of electron spin diffusion in the(110)-GaAs/(Al,Ga)As quantum well with low temperatures,we have made experimental and theoretical studies.The main aspects of this thesis include:(1)A detail description of the spin dynamics theory in semiconductors is given.It theoretically analyzes the structural properties of bulk GaAs semiconductor crystal and electronic band.We focus on the issue about the formation of GaAs/(Al,Ga)As two-dimensional electron gas structure.It also describes the structure of(110)-oriented GaAs/(Al,Ga)As quantum well in the thesis.Based on the pump-probe mechanism and the magneto-optical Kerr effect,we developed a high spatially resolved ultrafast magneto-optical Kerr measurement setup.It summarizes finite element method and functions of COMSOL Multiphysics simulation software,concluding basic steps of numerical simulations.(2)We use the ultrafast pump-probe technique which based on magneto-optical Kerr effect to measurement the electron spin diffusion dynamics of(110)-oriented GaAs/(Al,Ga)As quantum well with low temperatures.Based on a two-dimensional unipolar diffusion model,we numerically simulate the spin diffusion dynamics with experiment.For low temperatures,the simulation results show good consistence with experimental measurements in the regime of lower excitation densities.Experimental discrepancy is observed at short time delay for a high excitation density,and this may relate to various effects of hot carriers.