12,363 research outputs found
Diffusive Transport in Quasi-2D and Quasi-1D Electron Systems
Quantum-confined semiconductor structures are the cornerstone of modern-day
electronics. Spatial confinement in these structures leads to formation of
discrete low-dimensional subbands. At room temperature, carriers transfer among
different states due to efficient scattering with phonons, charged impurities,
surface roughness and other electrons, so transport is scattering-limited
(diffusive) and well described by the Boltzmann transport equation. In this
review, we present the theoretical framework used for the description and
simulation of diffusive electron transport in quasi-two-dimensional and
quasi-one-dimensional semiconductor structures. Transport in silicon MOSFETs
and nanowires is presented in detail.Comment: Review article, to appear in Journal of Computational and Theoretical
Nanoscienc
Electron mobility in surface- and buried- channel flatband In<sub>0.53</sub>Ga<sub>0.47</sub>As MOSFETs with ALD Al<sub>2</sub>O<sub>3</sub> gate dielectric.
In this paper, we investigate the scaling potential of flatband III-V MOSFETs by comparing the mobility of surface and buried In<sub>0.53</sub>Ga<sub>0.47</sub>As channel devices employing an Atomic Layer Deposited (ALD) Al<sub>2</sub>O<sub>3</sub> gate dielectric and a delta-doped InGaAs/InAlAs/InP heterostructure.
Peak electron mobilities of 4300 cm<sup>2</sup>/V·s and 6600 cm<sup>2</sup>/V·s at a carrier density of 3Ă1012 cm<sup>-2</sup> for the surface and buried channel structures respectively were determined. In contrast to similarly scaled inversion-channel devices, we find that mobility in surface channel flatband structures does not drop rapidly with electron density, but rather high mobility is maintained up to carrier concentrations around 4x10<sup>12</sup> cm<sup>-2</sup> before slowly dropping to around 2000 cm<sup>2</sup>/V·s at 1x10M<sup>13</sup> cm<sup>-2</sup>. We believe these to be world leading metrics for this material system and an important development in informing the III-V MOSFET device architecture selection process for future low power, highly scaled CM
The effect of low-energy ion-implantation on the electrical transport properties of Si-SiO2 MOSFETs
Using silicon MOSFETs with thin (5nm) thermally grown SiO2 gate dielectrics,
we characterize the density of electrically active traps at low-temperature
after 16keV phosphorus ion-implantation through the oxide. We find that, after
rapid thermal annealing at 1000oC for 5 seconds, each implanted P ion
contributes an additional 0.08 plus/minus 0.03 electrically active traps,
whilst no increase in the number of traps is seen for comparable silicon
implants. This result shows that the additional traps are ionized P donors, and
not damage due to the implantation process. We also find, using the room
temperature threshold voltage shift, that the electrical activation of donors
at an implant density of 2x10^12 cm^-2 is ~100%.Comment: 11 pages, 10 figure
Design space for low sensitivity to size variations in [110] PMOS nanowire devices: The implications of anisotropy in the quantization mass
A 20-band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding
model is used with a semi-classical, ballistic, field-effect-transistor (FET)
model, to examine the ON-current variations to size variations of [110]
oriented PMOS nanowire devices. Infinitely long, uniform, rectangular nanowires
of side dimensions from 3nm to 12nm are examined and significantly different
behavior in width vs. height variations are identified and explained. Design
regions are identified, which show minor ON-current variations to significant
width variations that might occur due to lack of line width control. Regions
which show large ON-current variations to small height variations are also
identified. The considerations of the full band model here show that ON-current
doubling can be observed in the ON-state at the onset of volume inversion to
surface inversion transport caused by structural side size variations. Strain
engineering can smooth out or tune such sensitivities to size variations. The
cause of variations described is the structural quantization behavior of the
nanowires, which provide an additional variation mechanism to any other
ON-current variations such as surface roughness, phonon scattering etc.Comment: 24 pages, 5 figure
Bandstructure Effects in Ultra-Thin-Body DGFET: A Fullband Analysis
This paper discusses a few unique effects of ultra-thin-body double-gate
NMOSFET that are arising from the bandstructure of the thin film Si channel.
The bandstructure has been calculated using 10-orbital
tight-binding method. A number of intrinsic properties including band gap,
density of states, intrinsic carrier concentration and parabolic effective mass
have been derived from the calculated bandstructure. The spatial distributions
of intrinsic carrier concentration and effective mass, arising from the
wavefunction of different contributing subbands are analyzed. A self-consistent
solution of Poisson-Schrodinger coupled equation is obtained taking the full
bandstructure into account, which is then applied to an insightful analysis of
volume inversion. The spatial distribution of carriers over the channel of a
DGFET has been calculated and its effects on effective mass and channel
capacitance are discussed.Comment: 13 pages, 21 figure
Electron Mobility and Magneto Transport Study of Ultra-Thin Channel Double-Gate Si MOSFETs
We report on detailed room temperature and low temperature transport
properties of double-gate Si MOSFETs with the Si well thickness in the range
7-17 nm. The devices were fabricated on silicon-on-insulator wafers utilizing
wafer bonding, which enabled us to use heavily doped metallic back gate. We
observe mobility enhancement effects at symmetric gate bias at room
temperature, which is the finger print of the volume inversion/accumulation
effect. An asymmetry in the mobility is detected at 300 K and at 1.6 K between
the top and back interfaces of the Si well, which is interpreted to arise from
different surface roughnesses of the interfaces. Low temperature peak
mobilities of the reported devices scale monotonically with Si well thickness
and the maximum low temperature mobility was 1.9 m2/Vs, which was measured from
a 16.5 nm thick device. In the magneto transport data we observe single and two
sub-band Landau level filling factor behavior depending on the well thickness
and gate biasing
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