Direct verification of the q-dependence of the Frِhlich interaction

The luminescence arising from the recombination of photoexcited hot electrons with neutral acceptor states in p-doped semiconductors and quantum wells is partly polarized because of the optical selection rules involved in the initial excitation and the recombination processes. For excitation with linearly polarized light, the photoelectrons are angularly distributed anisotropically in k-space, and this distribution determines the degree of linear polarization of the resulting luminescence. Scattering of the hot electrons by LO-phonon reduces their excess energy in discrete steps and degrades the initial structure in the angular distribution in k-space, reducing the degree of polarization of the luminescence. Measurements of this depolarization for electrons excited in specific k-directions are compared with calculations of that expected for various q-dependences of the electron–LO-phonon interaction, assuming that scattering is effectively by bulk GaAs phonons. The comparison directly demonstrates experimentally the validity of the generally accepted 1/q2 dependence of the widely important Fröhlich interaction, and illustrates the importance of luminescence polarization in investigating directional effects in hot electron dynamics.