Electron Spin Dynamics In ?-? Semiconductor Single Crystals

Group ?-? compounds CdS and ZnO are common wide band gap semiconductors and have important optoelectronic applications.They have a smaller spin-orbit coupling energy and are expected to obtain a longer spin relaxation time.In this thesis,the time-resolved Faraday / Kerr rotation spectroscopy technique is used to comprehensively study the electron spin coherence dynamics in n-type CdS single crystal and ZnO single crystal.The main research contents and results are as follows:(1)The electron spin coherence characteristics of hexagonal wurtzite n-type CdS single crystal at different temperatures and different laser wavelengths are systematically studied.Two types of electronic spin signals are observed at low temperature.One is a short-lived spin signal at shorter pump-probe wavelengths,with a spin dephasing time of ~40 ps.The spin signal can last up to room temperature and is almost unaffected by temperature.The other is a long-lived spin signal at longer pump-probe wavelengths,of which the spin dephasing time exceeds 4.8 ns at 5 K and decreases with increasing temperature.Studies reveal that long-lived spin signals are attributed to localized electrons,while short-lived spin signals are attributed to conduction delocalized electrons.(2)The electron spin coherence dynamics of hexagonal wurtzite n-type ZnO single crystal at different wavelengths,different magnetic fields,different pump light excitation powers,and different in-plane angles were studied at room temperature.It was found that the electron spin dephasing time is as long as 5.5 ns,which is much longer than the room temperature data reported in the literature for bulk ZnO.Studies have shown that the long-lived spin signal comes from the localized electrons in the crystal.