Miniband effects on hot-electron photoluminescence polarization in GaAs/AlAs superlattices

Abstract

We have studied the polarization properties of the hot electron photoluminescence (HEL) in GaAs/AlAs superlattices (SL's) and found that they are strongly affected by electron miniband formation. The quasi-three-dimensional motion of the SL electrons results in a dependence of the HEL polarization on their ratio of lateral and miniband kinetic energy. We discuss the effect of a magnetic field on the linear HEL polarization in the Faraday and Voigt geometries. Measurements in the Voigt geometry clearly demonstrate that the momentum distribution of photogenerated electrons is strongly anisotropic. The photogenerated electrons propagate predominantly along the SL growth direction when their kinetic energy is smaller than the electron miniband width or comparable to it. However, when their kinetic energy exceeds the miniband width electrons with lateral momenta dominate in the momentum distribution function. We present a theory of the HEL polarization in SL's and its magnetic field dependence which explains these observations.