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Title: Optimal Ge/SiGe nanofin geometries for hole mobility enhancement: Technology limit from atomic simulations

We use first principles simulations to engineer Ge nanofins for maximum hole mobility by controlling strain tri-axially through nano-patterning. Large-scale molecular dynamics predict fully relaxed, atomic structures for experimentally achievable nanofins, and orthogonal tight binding is used to obtain the corresponding electronic structure. Hole transport properties are then obtained via a linearized Boltzmann formalism. This approach explicitly accounts for free surfaces and associated strain relaxation as well as strain gradients which are critical for quantitative predictions in nanoscale structures. We show that the transverse strain relaxation resulting from the reduction in the aspect ratio of the fins leads to a significant enhancement in phonon limited hole mobility (7× over unstrained, bulk Ge, and 3.5× over biaxially strained Ge). Maximum enhancement is achieved by reducing the width to be approximately 1.5 times the height and further reduction in width does not result in additional gains. These results indicate significant room for improvement over current-generation Ge nanofins, provide geometrical guidelines to design optimized geometries and insight into the physics behind the significant mobility enhancement.
Authors:
; ; ; ;  [1] ;  [2]
  1. School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)
  2. School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)
Publication Date:
OSTI Identifier:
22402997
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 77 NANOSCIENCE AND NANOTECHNOLOGY; APPROXIMATIONS; ASPECT RATIO; COMPUTERIZED SIMULATION; ELECTRIC CURRENTS; ELECTRONIC STRUCTURE; GAIN; GERMANIUM; GERMANIUM SILICIDES; HOLE MOBILITY; HOLES; INTERFACES; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; PHONONS; RELAXATION; STRAINS; SURFACES