Coherent carrier propagation in the continuum of asymmetric quantum-well structures

In specific GaAs/Al(x)Ga(1-x)As quantum-well structures with a lack of inversion symmetry, the spectral dependence of the bound-to-continuum photocurrent shows sign reversals as a function of the excitation energy. These sign reversals can be explained in terms of coherently propagating carriers, which experience constructive or destructive interference according to their associated de Broglie wavelength. We show how a coherent control of the carrier motioning the continuum states can be achieved experimentally in appropriate quantum-well structures. A theoretical approach to simulate the observed current sign reversal is presented.