ENHANCEMENT OF THE ELECTRONIC EFFECTIVE-MASS IN QUANTUM WIRES

We show that the nonparabolicity and spin splitting enhance electron effective mass appreciably in a quantum wire. In bulk materials, these effects are usually small since electrons are near the conduction-band edges. In quantum wires, strong confinement puts the electrons far from the conduction-band edge, giving rise to large nonparabolicity effects. We derive a simple expression for the effective mass parallel to the transport direction in the quantum wire, taking into account the band nonparabolicity, anisotropy, and spin splitting. We apply our formalism to GaAs/Al0.3Ga0.7As quantum wires and find that the parallel mass could be 50% more than the bulk value for a wire width of 50 angstrom.