Raman-scattering from elementary excitations in GaAs with 'n-i-p-i' doping superlattices

The authors present results of spin-flip and non-spin-flip electronic Raman measurements on a GaAs with doping superlattice as a function of the non-equilibrium charge carrier concentration. They have been able to measure down to concentrations where only the lowest sub-band is appreciably populated. While the spin-flip excitation energies vary strongly with the light intensity (corresponding to varying superlattice potential), the lowest non-spin-flip excitations are almost unaffected, demonstrating the importance of screening. The measured light scattering resonances, are compared with self-consistently calculated electron-hole excitation energies. In calculating the non-spin-flip excitation energies, the coupling of the induced charge density fluctuation to the LO phonon of the host lattice was taken into account. Good agreement with the experimental data was obtained.