First-principles study of electron transport in ScN

Abstract

We investigate the conduction-band structure and electron mobility in rocksalt ScN based on density functional theory. The first-principles band structure allows us to obtain band velocities and effective masses as a function of energy. Electron-phonon scattering is assessed by explicitly computing the $q$-dependent electron-phonon matrix elements, with the inclusion of the long-range electrostatic interaction. The influence of free-carrier screening on the electron transport is assessed using the random phase approximation. We find a notable enhancement of electron mobility when the carrier concentration exceeds 10${}^{20}$ cm${}^{-3}$. We calculate the room-temperature electron mobility in ScN to be 587 cm${}^2$/Vs at low carrier concentrations. When the carrier concentration is increased, the electron mobility starts to decrease significantly around $n=10^{19}$ cm${}^{-3}$, and drops to 240 cm${}^2$/Vs at $n=10^{21}$ cm${}^{-3}$. We also explore the influence of strain in (111)- and (100)-oriented ScN films. For (111) films, we find that a 1.0\% compressive epitaxial strain increases the in-plane mobility by 72 cm${}^2$/Vs and the out-of-plane mobility by 50 cm${}^2$/Vs. For (100) films, a 1.0\% compressive epitaxial strain increases the out-of-plane mobility by as much as 172 cm${}^2$/Vs, but has a weak impact on the in-plane mobility. Our study sheds light on electron transport in ScN at different electron concentrations and shows how strain engineering could increase the electron mobility.

12 pages, 11 figures

References in corpus (5)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Exact-exchange based quasiparticle energy calculations for the band gap, effective masses and deformation potentials of ScN
• Theory of electron-plasmon coupling in semiconductors
• Giant polarization charge density at lattice-matched GaN/ScN interfaces