New approaches for first-principles modelling of inelastic transport in nanoscale semiconductor devices with thousands of atoms

Tue Gunst, Mads Brandbyge, Mattias Lau Nøhr Palsgaard, Troels Markussen, Kurt Stokbro

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

We present two different methods which both enable large-scale first-principles device simulations including electron-phonon coupling (EPC). The methods are based on Density Functional Theory and Nonequilibrium Greens Functions (DFT- NEGF) calculations of electron transport. The inelastic current is in both methods calculated in a post-processing step to a self consistent DFT calculation. The first method is based on first order perturbation theory in the EPC self-energy within the Lowest Order Expansion (LOE) approximation. The method requires calculation of the first-principles EPC in the device region and it includes the effect of each phonon mode on the current perturbatively. This approach is made practical by calculating the EPC of the device region using a smaller periodic reference system. In addition, the phonon modes are assembled into a small number of energy intervals in which phonon modes are described collectively. The second method involves calculating the electron transmission for a single configuration where the atoms are displaced according to the phonon temperature of the system. Thus, this method has a computational cost equivalent to conventional elastic transport calculations. Both methods have been implemented in the Atomistix ToolKit (ATK) and we apply the methods for calculating the inelastic current in a silicon n-i-n junction and for calculation of phonon limited mobilities of silicon nanowires.
Original languageEnglish
Title of host publication2017 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD)
Number of pages4
PublisherIEEE
Publication date2017
Pages13-16
ISBN (Electronic)978-4-86348-610-2
DOIs
Publication statusPublished - 2017
EventInternational Conference on Simulation of Semiconductor Processes and Devices 2017 - Kamakura, Japan
Duration: 7 Sept 20179 Sept 2017
Conference number: 22

Conference

ConferenceInternational Conference on Simulation of Semiconductor Processes and Devices 2017
Number22
Country/TerritoryJapan
CityKamakura
Period07/09/201709/09/2017

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