INTERBAND-TRANSITIONS OF SI DELTA-DOPED LAYERS IN PARA-TYPE GAAS

The two-dimensional (2D) electron gas present in Si-delta-doped layers in p-type GaAs is investigated through photoreflectance (PR) measurements performed at 300 and 77 K. The obtained spectra show oscillatory structures above the GaAs band gap which are ascribed to Franz-Keldysh oscillations. The decrease in the energy differences of the oscillations extrema with temperature indicates a reduction of the built-in electric field in the-delta-doped region. The values of the electric field extracted from the experimental data are compared with those obtained from theoretical calculations based on a simultaneous self-consistent solution of the Schrodinger and Poisson equations. The agreement between theory and experiment strongly indicate that the observed oscillatory structures in the PR spectra are due to transitions to electron states of the 2D electron gas.