Effect Of Optical Carriers On Spin Relaxation In A(110)-GaAs Quantum Well

The semiconductor spintronics,which is a combined subject of the semiconductor technology and quantum mechanical property based on spin,is an important field of condensed matter physics.The semiconductor spintronics is not only abundant in physical meaning,but also promotes the development of spintronics devices.The main purpose of semiconductor spintronics research is to use the electronic spin as the carrier of information,and to control the spin degree of freedom to develop a new generation of spin devices.A prerequisite to spintronics devices is that spin polarization should persist enough long time,so the study of electron spin dynamics has become one hot topic in the related research.In the experiment on(110)-orientated GaAs/(Al,GaAs)quantum well,we use the time-correlated single-photon counting(TCSPC)technique to measure the photoluminescence dynamics.The electron spin dynamics of(110)-orientated GaAs/(Al,Ga As)quantum well is investigated by two-color time-resolved Kerr rotation(TRKR)method.Then by two means experiment technique,the effect of optical carriers on electron spin relaxation is experimentally studied in GaAs/(Al,GaAs)quantum well.The main important results in the thesis are given as follows:(1)The photoluminescence dynamics in(110)-GaAs/(Al,GaAs)quantum well is investigated by TCSPC method at 20 K for different excitation density.It is found that the photoluminescence lifetime increase with excitation density as:(?).The density of excited optical carriers is estimated by measuring the photoluminescence lifetime and calculating the optical absorption.(2)The spin dynamics of(110)-GaAs/(Al,GaAs)quantum well is investigated by means of two-color TRKR technique at different excitation density.The spin relaxation time ?s versus pump power at 20 K is studied by experiments.In(110)-GaAs quantum well,the spin relaxation time decreases from ?s=4.9ns to ?s=1.4ns,while the pump power density increases from 4.2 W/cm2 to 140 W/cm2.With the increasing excitation power density,the more hole-electron pair is generated,we can conclude that a strong electron spin relaxation dynamic is dependent on hole density.(3)By determining the corresponding spin relaxation rate 1/?s from TRKR measuring and depending on the hole density Nh from the photoluminescence measuring,we can obtain the relation between 1/?s and Nh as a linear relationship.By calculating the theoretical dependency value of the relaxation rate and hole density contributed by the Bir-Aronov-Pikus mechanism,our experimentally determined value is good consistent with the theoretical calculation.Hence we quantitatively verify that the BAP mechanism is the dominant factor of the electron spin relaxation in(110)-GaAs/(Al,GaAs)quantum well.