Electron Mobility in Monoclinic \beta-Ga2O3 - Effect of Plasmon-phonon Coupling, Anisotropy, and Confinement

TL;DR

This study investigates electron mobility in monoclinic eta-Ga2O3, highlighting the effects of plasmon-phonon coupling, anisotropy, and confinement, and predicts high mobility in 2D electron gas configurations.

Contribution

It combines density functional perturbation theory, coupling calculations, and Boltzmann transport to analyze electron mobility, emphasizing plasmon-phonon interactions and anisotropy effects.

Findings

Bulk mobility of 182 cm2/V.s at high electron density

2DEG mobility of about 418 cm2/V.s with remote impurities

Anisotropy in mobility linked to IR active phonon modes

Abstract

This work reports an investigation of electron transport in monoclinic \beta-Ga2O3 based on a combination of density functional perturbation theory based lattice dynamical computations, coupling calculation of lattice modes with collective plasmon oscillations and Boltzmann theory based transport calculations. The strong entanglement of the plasmon with the different longitudinal optical (LO) modes make the role LO-plasmon coupling crucial for transport. The electron density dependence of the electron mobility in \beta-Ga2O3 is studied in bulk material form and also in the form of two-dimensional electron gas. Under high electron density a bulk mobility of 182 cm2/ V.s is predicted while in 2DEG form the corresponding mobility is about 418 cm2/V.s when remote impurities are present at the interface and improves further as the remote impurity center moves away from the interface. The trend of the electron mobility shows promise for realizing high electron mobility in dopant isolated electron channels. The experimentally observed small anisotropy in mobility is traced through a transient Monte Carlo simulation. It is found that the anisotropy of the IR active phonon modes is responsible for giving rise to the anisotropy in low-field electron mobility.