Carrier localization and enhanced spontaneous emission due to plasma nanosheath formation in polar nanostructured materials

The longitudinal component of the polarization field inherent in polar materials, combined with constrained carrier motion along the quantum wells, causes formation of equilibrium plasma nano-sheaths at intersections of quantum wells. The induced short range (nm) potentials of peak voltages much larger than the thermal carrier energy cause wavefunction localization, which further reduces the dimensionality of the carrier behavior. The associated energy band-bending causes enhanced carrier accumulation at quantum wedges and quantum tips formed by intersecting quantum wells. In addition, the total carrier number over the QW length increases, manifesting spontaneous intrinsic pumping due to polarization. As a result, the spontaneous emission is localized at quantum wedges, and the total emission exceeds that from a flat quantum well of similar parameters, as experimentally observed. The sheath potentials are sufficiently high for 1-D or 0-D carrier localization at quantum wedges and quantum tips.