Photoreflectance study of barrier-width dependence of above-barrier states in GaAs-AlxGa1-xAs multiple quantum wells

The optical transitions of the quasibound states at the above-barrier region in GaAs/Ga0.77Al0.23As multiple quantum wells have been observed at room temperature by photoreflectance measurement. It is found that the barrier-width dependence of the above-barrier transition energies can be described quite well by the modified Messiah's calculation. However, the simple calculation using the constructive interference condition can only explain the transitions at lower energies, and fails with increasing transition energy.