Abstract:We investigate the spin-resolved dynamics of spin-polarized carriers injected via a ferromagnetic scanningtunnelling-microscope tip (STM tip) into uniformly and non-uniformly n-doped bulk semiconductor -externally driven by a current source. We propagate the injected spin packets (assumed gaussian in space at t = 0) by considering a spin hydrodynamic approach based on balance equations directly derived from a spin-dependent Boltzmann equation. We determine the spin-polarization landscapes (time and position) o… Show more
“…Under these approximations, it is possible to obtain explicit solutions for the two-temperature approach and the excess of the carrier density however, they are lengthy expressions to be shown here, see Ref. [16], and we restrict ourselves to give the plots of the amplitude of the temperature field as a function of the modulation frequency.…”
Section: Resultsmentioning
confidence: 99%
“…The solution of this set of equations allows us to determine the dynamic contribution to the temperature and carrier distribution in the semiconductor. The analytical expressions for the temperature and carrier concentration are too complicated to be shown here [16]. We restrict ourselves to present the relevant physics of the work within some physical approximations.…”
PACS 66.70.+f, 72.20.Jv, 82.80.Kq The electron, hole, and phonon temperatures are calculated in semiconductors by taking into account the finite carrier diffusion and nonradiative recombination time in the sample. We assume that the energy of the modulated excitation radiation is greater than the energy gap and absorbed at the surface of the semiconductor, therefore, a source of heat and carrier generation at the surface of the sample are time dependent and must be considered in the photothermal theory. Under this situation, the coupled one-dimensional heat transport (for each quasiparticle system) and carrier diffusion equations in the strong hole-phonon energy interaction approximation and charge quasineutrality condition are solved. Since the nonequilibrium carrier concentration depends sensitively on the electron and phonon fluctuation temperature, the heat power density generated in the sample due to the recombination of the electron-hole pair will be greatly influenced by the inhomogeneous quasiparticle temperature distributions. This latter effect comes through the recombination rate of carriers and it will be considered in the photothermal signal.
“…Under these approximations, it is possible to obtain explicit solutions for the two-temperature approach and the excess of the carrier density however, they are lengthy expressions to be shown here, see Ref. [16], and we restrict ourselves to give the plots of the amplitude of the temperature field as a function of the modulation frequency.…”
Section: Resultsmentioning
confidence: 99%
“…The solution of this set of equations allows us to determine the dynamic contribution to the temperature and carrier distribution in the semiconductor. The analytical expressions for the temperature and carrier concentration are too complicated to be shown here [16]. We restrict ourselves to present the relevant physics of the work within some physical approximations.…”
PACS 66.70.+f, 72.20.Jv, 82.80.Kq The electron, hole, and phonon temperatures are calculated in semiconductors by taking into account the finite carrier diffusion and nonradiative recombination time in the sample. We assume that the energy of the modulated excitation radiation is greater than the energy gap and absorbed at the surface of the semiconductor, therefore, a source of heat and carrier generation at the surface of the sample are time dependent and must be considered in the photothermal theory. Under this situation, the coupled one-dimensional heat transport (for each quasiparticle system) and carrier diffusion equations in the strong hole-phonon energy interaction approximation and charge quasineutrality condition are solved. Since the nonequilibrium carrier concentration depends sensitively on the electron and phonon fluctuation temperature, the heat power density generated in the sample due to the recombination of the electron-hole pair will be greatly influenced by the inhomogeneous quasiparticle temperature distributions. This latter effect comes through the recombination rate of carriers and it will be considered in the photothermal signal.
Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. While metal spintronics has already found its niche in the computer industry-giant magnetoresistance systems are used as hard disk read heads-semiconductor spintronics is yet to demonstrate its full potential. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent interaction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In view of the importance of ferromagnetic semiconductor materials, a brief discussion of diluted magnetic semiconductors is included. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field. 72.25.Rb, 75.50.Pp,
PACS
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