Photoreflectance analysis of MQW in intermediate electric field regime

Photoreflectance spectra of MBE grown GaAsAlGaAs MQWs in an intermediate electric field regime are analyzed by using a lineshape model accounting for both bulk and multilayer contributions to the ΔR/R signal. The experimental spectra exhibiting the simultaneous presence of both Franz-Keldysh oscillations and quantum confinement related structures in the same spectral energy range (1.4-1.7 eV) were fitted to a lineshape model consisting of a linear combination of a modified version of the Aspnes asymptotic expression for subsidiary oscillations and first derivative functional forms typical of exciton photoreflectance in quasi-bidimensional systems. By comparing the optical data obtained in different surface field conditions it is shown that the proposed analytical procedure allows reliable information on MQW parameters to be obtained even when the spurious signal due to subsidiary oscillations originating in the buffer or substrate, is much greater than the optical response associated with quantum confinement