Gated Si nanowires for large thermoelectric power factors

Journal Article · Mon Aug 18 04:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4893977· OSTI ID:22311345

Neophytou, Neophytos ^[1]; Kosina, Hans ^[2]

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1. School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom)
2. Institute for Microelectronics, Vienna University of Technology, Gusshausstrasse 27-29/E360, Vienna A-1040 (Austria)

We investigate the effect of electrostatic gating on the thermoelectric power factor of p-type Si nanowires (NWs) of up to 20 nm in diameter in the [100], [110], and [111] crystallographic transport orientations. We use atomistic tight-binding simulations for the calculation of the NW electronic structure, coupled to linearized Boltzmann transport equation for the calculation of the thermoelectric coefficients. We show that gated NW structures can provide ∼5× larger thermoelectric power factor compared to doped channels, attributed to their high hole phonon-limited mobility, as well as gating induced bandstructure modifications which further improve mobility. Despite the fact that gating shifts the charge carriers near the NW surface, surface roughness scattering is not strong enough to degrade the transport properties of the accumulated hole layer. The highest power factor is achieved for the [111] NW, followed by the [110], and finally by the [100] NW. As the NW diameter increases, the advantage of the gated channel is reduced. We show, however, that even at 20 nm diameters (the largest ones that we were able to simulate), a ∼3× higher power factor for gated channels is observed. Our simulations suggest that the advantage of gating could still be present in NWs with diameters of up to ∼40 nm.

• OSTI ID: 22311345
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 7 Vol. 105; ISSN APPLAB; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
BOLTZMANN EQUATION
CARRIER MOBILITY
CHARGE CARRIERS
DOPED MATERIALS
ELECTRONIC STRUCTURE
HOLES
LAYERS
MODIFICATIONS
NANOWIRES
POWER FACTOR
QUANTUM WIRES
ROUGHNESS
SIMULATION
SURFACES
THERMOELECTRICITY