New Method for Reliable and Efficient Calculations of Resistivity & Mobility

Posted on August 21, 2017

A new paper using QuantumATK has been published in Phys. Rev. B [1] as a product of collaboration between Synopsys QuantumATK group and a group of researchers at the Technical University of Denmark. The paper presents a new method, MD-Landauer, combining Green's function transport and molecular dynamics (MD) for reliable and efficient calculations of resistivity and mobility including the effect of electron-phonon couplings (EPCs), which plays a central role in the performance of most electronic devices.

The MD-Landauer approach is validated against experimental results and state-of-the-art calculations using the Boltzmann Transport Equation (BTE) method [2] for a variety of systems: Si and Au nanowires, Si and Au bulk, Carbon Nano Tubes (CNTs) and graphene (see Fig 1). The calculated mobilities and resistivities agree semi-quantitatively with those calculated using the BTE method and with experiments, and trends are correctly reproduced. This shows that the MD-Landauer method is an appealing alternative to BTE to treat EPCs in large and complex (for example, non-crystalline, with defects and substitutions) systems. Full-scale Density Functional Theory electron-phonon calculations are just starting to become available as a method, and the MD-Landauer approach makes them much more reasonable in terms of computation time.

Fig.1.Schematic illustration of the workflow of the MD-Landauer method: 1. A number (10-50) of MD trajectories are equilibrated at a target temperature using a random Maxwell-Boltzmann distribution of initial velocities  to create an ensemble of snapshots of the structure at that temperature. 2. The electronic transmission is calculated for all the snapshots using the DFT+NEGF approach and the resulting transmission functions are averaged to obtain the finite temperature transmission. 3. The temperature-dependent resistivities can be obtained from finite temperature transmission. 4. Mobilities can be obtained from the calculated resistivities and the density of states.

Relevant Resources

References

[1] T. Markussen, M. Palsgaard, D. Stradi, T. Gunst, M. Brandbyge and K. Stokbro, "Electron-phonon scattering from Green's function transport combined with molecular dynamics: Applications to mobility predictions", Phys. Rev. B 95, 245210 (2017). arXiv, pages 1701.02883v1, 2017. URL: arXiv:1701.02883.

[2] T. Gunst, T. Markussen, K. Stokbro and M. Brandbyge, "First-principles method for electron-phonon coupling and electron mobility: Applications to two-dimensional materials", Phys. Rev. B 93, 035414 (2016).

arXiv, pages 1511.02045v1, 2017. URL: arXiv:1511.02045.

[3] T. Gunst, T. Markussen, M. L. N. Palsgaard, K. Stokbro and M. Brandbyge, “First principles electron transport with phonon coupling: Large scale at low cost”, Phys. Rev. B 96, 161404 (R) (2017) arXiv, pages 1706.09290, 2017. URL: arXiv:1706.09290.

Interested in applying QuantumATK software to your research? Test our software or contact us at quantumatk@synopsys.com to get more information on QuantumATK platform for atomic-scale modeling.