EFFECTS OF AN ELECTRIC-FIELD ON THE CONTINUUM ENERGY-LEVELS IN INXGA1-XAS GAAS QUANTUM-WELLS TERMINATED WITH THIN CAP LAYERS/

Electroreflectance was used to study the influence of an electric fiel d on the bound and the continuum states of InxGa1-xAs/GaAs quantum-wel l structures of various well widths, terminated by thin cap layers. Op tical transitions involving only bound states were not significantly a ffected for the cap-layer thicknesses studied, and are Stark shifted a s expected by the electric field. However, strong oscillations are obs erved in the spectra at energies larger than the barrier band gap, and are due to quantum interference in the continuum state wave functions which is related to the finite size of the cap layer. These oscillati ons, which do not follow a Franz-Keldysh relation, shift linearly with the electric field.