Hot electron luminescence spectroscopy of GaAs shows polarization dependent lineshape variations of 0.5 approximately 1.0 meV. It is shown how a lineshape model which includes a k.p calculation of the band structure, optical transition matrix elements in the dipole model, and lifetime broadening, is able to explain these polarization effects. For linearly polarized excitation, the observation arises from the optical alignment of the hot electron momenta, while for circularly polarized excitation the effect is caused by transitions between specific electronic spin states identifiable by a selection rule.
STRACT We use Raman scattering to investigate direct gap Si/Ge superlattices for which the Si layers are in the form of biatomic sheets. We find a characteristic signal arising from the presence of the biatomic Si sheets. A range of samples have been investigated and 3-dimensional lattice dynamical calculations have been performed which pinpoint the Si layers as the origin of the signal. We illustrate how the signal may be used to characterise the quality of for example (Si)2/(Ge)6 superlattices grown at various substrate temperatures.
We show that electronic Raman scattering measurements of the intrasubband plasmon dispersion in a GaAs/A1GaAs heterojunction is a viable contactless optical method for the determination of sheet carrier density of the two-dimensional electron gas. We demonstrate non-persistent optical control of the carrier density by a dynamic charge transfer effect: from Raman measurements of the plasmon we directly determine the change in carrier concentration with excess illumination.
We deduce the F-L intervalley and poiar optic phonon scattering times of hot electrons in bulk GaAs from cw hot (e, A°)
luminescence spectra as a function of electron kinetic energy at low excitation densities. We obtain the lifetime broadening
due to these two processes from comparison with lineshape calculations using a 16x16 k.p Hamiltonian, a full integration
over k-space and a dipole model for the optical matrix elements. We find for the LO-phonon emission time tLO=(l32±lO)fS.
The threshold for IT-*L scattering is determined as (330±1O)meV, above which a distinct decrease in total lifetime is observed.
Minimum F÷L scattering times are l5Ofs to 200fs. We discuss an estimation for the deformation potential DTL.