Dynamics of dense spin ensemble excited in a barrier layer and detected in a well

Abstract

Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier layer and eventually quenches irradiatively in a GaAs quantum well (QW). A highest PL circular polarization of 30% can be kept at temperatures up to 120 K, while its room temperature value reaches about 17%. It is found that the main features of the optical spin orientation in bulk Al_0.27Ga_0.73As materials can be reproduced in terms of the wavelength dependence of PL polarization degree, as the spin polarized ensemble transfers and relaxes into GaAs QW. The transient of PL polarization degree also indicates that a dense spin ensemble collected from the barrier region is in favor of conserving its polarization in GaAs QW as evidenced by a rising temporal response.