Optical studies of perpendicular transport in semiconductor superlattices

Optical studies of perpendicular transport of carriers in superlattices are reviewed. Steady-state optical measurements demonstrate the existence of perpendicular transport in superlattices. The nature of the transport has been recently investigated by using all-optical time-of-flight techniques. These studies have demonstrated that the transport for both electrons and holes indeed proceeds by extended Bloch states of the minibands in short-period superlattices. Furthermore, the mobility for such transport has been determined by these ultrafast luminescence techniques. The transition from Bloch transport to the localized transport with increasing period of the superlattice has been directly observed.>