On the possibility of a direct observation of the time evolution in heterostructure barrier tunneling.

By varying two parameters of epitaxial growth, such as the width of a quantum well (QW) and its chemical composition, it is possible to design two QW's with identical ground-state levels in the conduction band - but different in the valence band. This allows a selective "preparation" of an initial electron state by interband photoexcitation. In a coupled QW system the electron will oscillate between the two wells, giving rise to an oscillating luminescence signal.