Differential photoreflectance from δ-doped structures and GaAs/n-GaAs interfaces

Using a differential modulation technique we suppress the perturbation of the surface electric field of the sample and extract photoreflectance from buried interfaces. The resulting signals show combinations of a low-field GaAs signature and a high-field oscillatory signal which suggest existence of an ∼30 meV potential offset at the highly doped GaAs/n-GaAs interfaces. The offset is present at both, δ-doped interfaces and simple doped interfaces. For low differential modulation intensities, we observe a signal which could be attributed to two-dimensional electron gas in δ-doped samples, however, the signal cannot be easily differentiated from low-field Franz-Keldysh oscillations.