Large Thermoelectric Power Factor in P-type Si (110)/[110] Ultra-Thin-Layers Compared to Differently Oriented Channels

TL;DR

This study demonstrates that p-type silicon ultra-thin layers with (110) surface orientation and [110] transport direction exhibit significantly enhanced thermoelectric power factors, especially at reduced thicknesses, due to favorable electronic properties and confinement effects.

Contribution

It reveals that (110) oriented channels in ultra-thin silicon layers outperform other orientations in thermoelectric power factor, highlighting optimal geometries for thermoelectric device design.

Findings

(110) channels have over 2X higher power factor than other orientations.

Power factor increases by ~40% as layer thickness decreases.

(110) surface confinement reduces sensitivity to surface roughness effects.

Abstract

Using atomistic electronic structure calculations and Boltzmann semi-classical transport we compute the thermoelectric power factor of ultra-thin-body p-type Si layers of thicknesses from W=3nm up to 10nm. We show that the power factor for channels in [110] transport orientation and strong (110) surface confinement largely outperforms all differently oriented channels by more than 2X. Furthermore, the power factor in this channel increases by ~40% with layer thickness reduction. This increase, together with the large confinement effective mass of the (110) surface, make this particular channel less affected by the detrimental effects of enhanced surface roughness scattering and distortion at the nanoscale. Our results, therefore, point towards the optimal geometrical features regarding orientation and length scale for power factor improvement in 2D thin-layers of zincblende semiconductors.