Quasi-ballistic, nonequilibrium electron distribution in inhomogeneous semiconductor structures

We report on a study of quasi-ballistic transport in deep submicron, inhomogeneous semiconductor structures, focusing on the analysis of signatures found in the full nonequilibrium electron distribution. We perform self-consistent numerical calculations of the Poisson-Boltzmann equations for a model n(+)-n(-)-n(+) GaAs structure and realistic, energy-dependent scattering. We show that, in general, the electron distribution displays significant, temperature dependent broadening and pronounced structure in the high-velocity tail of the distribution. The observed characteristics have a strong spatial dependence, related to the energy-dependence of the scattering, and the large inhomogeneous electric field variations in these systems. We show that in this quasi-ballistic regime, the high-velocity tail structure is due to pure ballistic transport, whereas the strong broadening is due to electron scattering within the channel, and at the source(drain) interfaces.Comment: 4 pages, 2 figure

Medial Architecture: "Points of View" about Architectural Media and Portrait Films - Based on the "Tizenkét kőmíves" project

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Spin-3/2 physics of semiconductor hole nanowires: Valence-band mixing and tunable interplay between bulk-material and orbital bound-state spin splittings

We present a detailed theoretical study of the electronic spectrum and Zeeman splitting in hole quantum wires. The spin-3/2 character of the topmost bulk-valence-band states results in a strong variation of subband-edge g factors between different subbands. We elucidate the interplay between quantum confinement and heavy-hole - light-hole mixing and identify a certain robustness displayed by low-lying hole-wire subband edges with respect to changes in the shape or strength of the wire potential. The ability to address individual subband edges in, e.g., transport or optical experiments enables the study of holes states with nonstandard spin polarization, which do not exist in spin-1/2 systems. Changing the aspect ratio of hole wires with rectangular cross-section turns out to strongly affect the g factor of subband edges, providing an opportunity for versatile in-situ tuning of hole-spin properties with possible application in spintronics. The relative importance of cubic crystal symmetry is discussed, as well as the spin splitting away from zone-center subband edges.Comment: 16 pages, 12 figures, RevTe