We demonstrate theoretically that spin dynamics of electrons injected into a GaAs semiconductor structure through a Schottky barrier possesses strong non-equilibrium features. Electrons injected are redistributed quickly among several valleys. Spin relaxation driven by the spin-orbital coupling in the semiconductor is very rapid. At T = 4.2 K, injected spin polarization decays on a distance of the order of 50 -100 nm from the interface. This spin penetration depth reduces approximately by half at room temperature. The spin scattering length is different for different valleys. Introduction.Electrical spin injection into a non-magnetic semiconductor structure is one of the most complicated issues in design of semiconductor spintronic devices [1][2][3]. High efficiency of spin injection in magnetic/nonmagnetic semiconductor structures has been demonstrated in the diffusive transport regime [4]. Also, in the ballistic transport regime, spin filtering with a magnetic semiconductor can lead to nearly 100% spin injection [5]. However, at the present stage spin-dependent properties of most of magnetic semiconductors are limited by the low temperature regime only, that strongly restricts their device application. Ferromagnetic metal contacts possess much higher Curie temperature and are more attractive for the application in room temperature spintronic devices. But, in conventional ohmic metal/semiconductor contacts large conductance mismatch [6] prevents efficient injection of spin polarized carriers. One of the solutions

An approach is proposed to project thermal behavior in a semiconductor integrated-circuit structure onto a functional space based on the proper orthogonal decomposition (POD). The approach substantially reduces the numerical degrees of freedom (DOF) needed for thermal simulations and requires no assumptions about physical geometry, dimensions, or heat flow paths. The POD approach is applied to a multi-fin FinFET structure having heat sources driven by power pulse excitations with time shifts, width variations, and amplitude modulations. The POD models were compared with detailed numerical simulations (DNS) and it was shown that the POD approach provides thermal solutions that were as accurate and detailed as the DNS. It offers a reduction in numerical DOFs by nearly six orders of magnitude to capture the peak temperatures in multi-fin FinFETs.Index Terms-Compact thermal model (CTM), FinFET, proper orthogonal decomposition (POD), reduced-order model (ROM), thermal simulation.

Abstract-We investigate effect of a step-doping profile on the spin injection from a ferromagnetic metal contact into a semiconductor quantum well (QW) in spin FETs using a Monte Carlo model. The considered scheme uses a heavily doped layer at the metal/semiconductor interface to vary the Schottky barrier shape and enhance the tunneling current. It is found that spin flux (spin current density) is enhanced proportionally to the total current, and the variation of current spin polarization does not exceed 20%.