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Simulation of spin field effect transistors: Effects of tunneling and spin relaxation on performance
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10.1063/1.3496666
/content/aip/journal/jap/108/8/10.1063/1.3496666
http://aip.metastore.ingenta.com/content/aip/journal/jap/108/8/10.1063/1.3496666
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

The spinFET schematic. The source and drain are HMF. The magnetization of the drain can be switched to obtain the parallel and antiparallel configurations of the two contacts. The double metal gates control the channel electrostatics. The source contact injects and the drain contact detects spin polarized current through oxide tunneling barriers. A spin randomization layer exists at the boundary of the HMF.

Image of FIG. 2.
FIG. 2.

plots for (a) parallel and (b) antiparallel configurations in ballistic transport regime. The gate voltage values are 0.7, 0.5, 0.3, and 0.1 V, from top to bottom curves.

Image of FIG. 3.
FIG. 3.

Magnetocurrent ratio of the ballistic spinFET under different drain bias. The dots are the data obtained as or 0.7 V, and a fitted curve is plotted to represent the average values of the discrete dots.

Image of FIG. 4.
FIG. 4.

Energy-position resolved current in the channel for (a) up-spin and (b) down-spin in the parallel configuration. Up-spins convert to down-spins as the electrons traverse the device.

Image of FIG. 5.
FIG. 5.

Energy-position resolved local density of state in the channel in parallel configuration. The spin-flip coupling constants are in (a), in (b), and in (c), which corresponding to 40 ps, 0.4 ps, and 1 fs spin-flip times, respectively. The strong coupling reduces the spin-flip time, and also broadens the available states in the channel.

Image of FIG. 6.
FIG. 6.

Energy-position resolved charge density in the channel in parallel configuration. The channel spin-flip coupling constants and injection efficiencies are: (100 ps spin-flip time) and 90% in (a) and (0.1 ps spin-flip time) and 60% in (b). The energy band edge for up-spin is shown. It is obvious that the energy band edges and charge density are different in these two scenarios.

Image of FIG. 7.
FIG. 7.

plots for (a) parallel and (b) antiparallel configurations in scattering transport regime. The gate voltage values are 0.7, 0.5, 0.3, and 0.1 V, from top to bottom curves. The spin-flip coupling constant is , which corresponds to 1 ps spin-flip time in the channel.

Image of FIG. 8.
FIG. 8.

Magnetocurrent ratio of spinFETs with spin scattering under different drain bias and with different spin-flip coupling constants. The symbols are for simulation results at (solid) or 0.7 V (open) and fitted curves are plotted to represent the median values of the two cases.

Image of FIG. 9.
FIG. 9.

Current-energy plot in antiparallel configuration for up-spin (majority, solid line) and down-spin (minority, dashed line) current at different as . Very small amount of current increase is seen as increase from 0.1 to 0.4 V [(a) to (b)]. A large amount of up-spin current flows as rises past 0.3 V as in (c).

Image of FIG. 10.
FIG. 10.

Energy-position resolved charge density of up-spin [(a) and (c)] and down-spin [(b) and (d)] current, for scattering [(a) and (b)], and ballistic [(c) and (d)] transport regimes. In the scattering transport regimes, the up-spins turn to down-spins and escape to the drain, while no down-spins current flows in the ballistic case.

Image of FIG. 11.
FIG. 11.

Magnetocurrent ratio of the spinFETs with spin scattering and interface spin scattering under different drain bias and with different interface spin-flip coupling constants. The channel spin-flip coupling is (10 ps spin-flip time). The symbols are for simulation results at (solid) or 0.7 V (open) and fitted curves are plotted to represent the median values of the two cases.

Image of FIG. 12.
FIG. 12.

Spin polarization along the channel with different interface spin-flip coupling constant and same channel scattering constant (solid line). The empirical parameter adjusts the spin injection efficiency, while controls the spin scattering along the channel.

Image of FIG. 13.
FIG. 13.

, plots of up-spin [(a) and (c)] and down-spin [(b) and (d)] current, for parallel [(a) and (b)], and antiparallel configuration [(c) and (d)]. The spin-flip coupling gives large up-spin current at the on-state and large down-spin current at medium in the antiparallel configuration.

Image of FIG. 14.
FIG. 14.

Energy-position resolved charge density of the (a) up-spin and the (b) down-spin current in the scattering transport at the on-state in the antiparallel configuration. The high pushes down the drain energy band, which gives a large amount of up-spin current flowing out of drain.

Image of FIG. 15.
FIG. 15.

Energy-position resolved charge density of the (a) up-spin and the (b) down-spin current in the scattering regime at the on-state. The source and drain are antiparallel configured. The high pushes down the drain energy band, but the large spin splitting blocks the electrons from going into the drain, which reduces the current at the on-state.

Image of FIG. 16.
FIG. 16.

Energy-position resolved charge density of the down-spin current in the scattering regime. The source and drain are antiparallel configured. The tunneling barrier for the down-spin electrons between the channel and drain can lower the total current and, therefore, increase MR by about .

Image of FIG. 17.
FIG. 17.

Magnetocurrent ratio of the spinFETs with various tunneling barriers configurations under different drain bias. The tunneling barriers in the source and drain ends are of 4 nm thick and 0.6 eV high. There are three devices simulated here: without tunneling barriers for both up- and down-spins (dashed line), with the same tunneling barriers for both spins (dotted line), and with the different barriers for both spins (solid line).

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/content/aip/journal/jap/108/8/10.1063/1.3496666
2010-10-18
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Simulation of spin field effect transistors: Effects of tunneling and spin relaxation on performance
http://aip.metastore.ingenta.com/content/aip/journal/jap/108/8/10.1063/1.3496666
10.1063/1.3496666
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