Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 44: Poster II
HL 44.1: Poster
Donnerstag, 11. März 2004, 16:30–19:00, Poster A
Unified Description of Spin-Polarized Electron Transport in Ferromagnet-Semiconductor Structures — •U. Wille and R. Lipperheide — Abteilung Theoretische Physik (SF5), Hahn-Meitner-Institut Berlin, Glienicker Str. 100, D-14109 Berlin, Germany
Generalizing our recent work [PRB 68, 115315 (2003)] on electron transport in semiconductor structures, we develop a unified description of ballistic and diffusive spin-polarized transport in ferromagnet-semiconductor structures. A “thermoballistic” current is introduced, in which electrons move ballistically in the band edge potential of the semiconductor, and are thermalized at certain randomly distributed equilibration points. Spin relaxation is allowed to occur in the ballistic intervals between the equilibration points. An integral equation for the density spin polarization in the semiconductor is derived. For constant band edge potential, this equation can be converted to a differential equation, which is identical to the spin diffusion equation, except that the spin diffusion length is renormalized by the factor (1+τ/τs)−1/2, where τ and τs are the momentum and spin relaxation times, respectively. The ballistic element in the unified description gives rise to discontinuities in the chemical potential at the ferromagnet-semiconductor interfaces. The spin polarization injected into the semiconductor and the position dependence of the polarization inside the semiconductor are obtained for any value of the ratio τ/τs.