Photoreflectance lineshape analysis of the selectively-doped GaAs/Al_0.3Ga_0.7As microstructure

The photoreflectance spectra of the selectively-doped GaAs/Al_0.3Ga_0.7As microstructure have been studied at various temperatures. The spectra contained two sets of oscillatory features above the gap of GaAs, and one set above the gap of Al_0.3Ga_0.7As. The sources of different features in the spectra were identified by comparing the spectra after different layers were etched off. The magnitudes of the internal fields were obtained from the band bendings near the surface or interfaces. A multilayer model with a different electric field in each layer was used to take into account the depth dependence of the dielectric functions due to different materials and the electric fields in the space-charge regions. The calculated lineshapes agree well with the observed photon modulated reflectance spectra.