Tunneling effects upon resonant-Raman-scattering intensities in GaAs/AlAs superlattices

We report sharp decreases in the resonant LO Raman intensity of GaAs/AlAs superlattices at the applied electric fields where the electrons can tunnel or transfer resonantly out of the wells. This is explained by a reduction of the exciton dephasing lifetime (i.e., increase in homogeneous linewidth). In particular, we observe a sharp drop at low fields due to tunneling to the first electron level confined in the adjacent well and another at high field due to transfer to the X point in the neighboring AlAs barriers. By tuning the photon energy we study Γ-X transfer from different states within the inhomogeneously broadened exciton line.