Excess conductance of superconductor-semiconductor interfaces due to phase conjugation between electrons and holes

A semiclassical description is given of charge transport through a superconductor-semiconductor interface. As a result of the presence of a potential barrier both Andreev and normal reflection occur. Elastic scatterers in the semiconductor generate multiple reflections at the interface. The constructive quantum interference which results from the phase conjugation between electrons and holes enhances the (differential) conductance above its classical value. This excess conductance is suppressed by a magnetic field, or by a finite energy. The latter can be due to a finite voltage bias or a finite temperature.