Subband Engineering for p-type Silicon Ultra-Thin Layers for Increased Carrier Velocities: An Atomistic Analysis

Neophytos Neophytou, Institute for Microelectronics, TU Wien, Austria
Gerhard Klimeck, NCN, Purdue University

Date of this Version



Journal of Applied Physics 109, 053721 (2011)


Copyright (2011) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 109, 053721 (2011) and may be found at The following article has been submitted to/accepted by Journal of Applied Physics. Copyright (2011) Neophytos Neophytou, Gerhard Klimeck, and Hans Kosina. This article is distributed under a Creative Commons Attribution 3.0 Unported License.


Ultra-thin-body (UTB) channel materials of a few nanometers in thickness are currently considered as candidates for future electronic, thermoelectric, and optoelectronic applications. Among the features that they possess, which make them attractive for such applications, their confinement length scale, transport direction, and confining surface orientation serve as degrees of freedom for engineering their electronic properties. This work presents a comprehensive study of hole velocities in p-type UTB films of widths from 15 nm down to 3 nm. Various transport and surface orientations are considered. The atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used for the electronic structure, and a semiclassical ballistic model for the carrier velocity calculation. We find that the carrier velocity is a strong function of orientation and layer thickness. The (110) and (112) surfaces provide the highest hole velocities, whereas the (100) surfaces the lowest velocities, almost 30% lower than the best performers. Additionally, up to 35% velocity enhancements can be achieved as the thickness of the (110) or (112) surface channels is scaled down to 3 nm. This originates from strong increase in the curvature of the p-type UTB film subbands with confinement, unlike the case of n-type UTB channels. The velocity behavior directly translates to ballistic on-current trends, and correlates with trends in experimental mobility measurements. VC 2011 American Institute of Physics. [doi:10.1063/1.3556435]


Nanoscience and Nanotechnology