Analogies Between Coherent Optical Interactions and Quantum Transport in Semiconductor Devices

Abstract

The new generations of ultrasmall semiconductor devices are characterized both by very short transit times of the carriers from source to drain of less than a picosecond and by very high electric fields of up to some 10⁶ V/cm. Under such conditions, carriers reach very high energies and are subjected to time scales (for example imposed by phonon scattering) of the order of 100 femtoseconds. Energy nonconserving and collisionally broadened transitions and the influence of the field during the collision (intracollisional field effect) strongly influence the transport behaviour¹. It is hard to treat such problems in a full spacedependent quantum mechanical theory. The necessary approximations become very serious and at the very end it is hard to recognize whether the final result still contains characteristic information or is dominated by the approximations. Furthermore specific experiments in devices are very hard to accomplish and measurements often allow for different interpretations.