Quantum transport anomalies in semiconductor nanosystems

We present quantum transport anomalies in the theoretical conductance of various semiconductor nanostructures. We first investigate a quantum channel with a chain of quantum boxes connected by slits, called a superlattice structure, and study the miniband and minigap effects associated with resonances and anti-resonances in the conductance. We also report studies of electron transport in a quantum wire containing series or parallel slits and a detector slit. In these systems, strong conductance oscillations due to quantum interference effects are predicted as a detector slit is moved across the wire. In the case of a single and multi-series slits, we attribute these effects to multiple reflections of the phase-coherent electron along the quantum wire. The transmission coefficients and electronic phase shifts are examined, which provide insights into the origins of these conductance oscillations. In the case of multi-parallel slits, peaks with two- (four-) fold splitting in the conductance are exhibited due to the quantum branch interference between the two (four) alternative electron paths. We also study the conductance of a quantum structure containing an artificially produced impurity. It is shown that the conductance modulations are strong when the impurity is scanned across the channel. We explain these oscillatory features of the conductance by a simple optical interference model and a simple adiabatic model. (C) 1995 American Institute of Physics.