By systematically comparing experimental and theoretical transport properties, we identify the polar optical phonon scattering as the dominant mechanism limiting electron mobility in β–Ga2O3 to <200 cm2/V s at 300 K for donor doping densities lower than ∼1018 cm–3. Despite similar electron effective mass of β–Ga2O3 to GaN, the electron mobility is ∼10× lower because of a massive Fröhlich interaction, due to the low phonon energies stemming from the crystal structure and strong bond ionicity. Based on the theoretical and experimental analysis, we provide an empirical expression for electron mobility in β–Ga2O3 that should help calibrate its potential in high performance device design and applications.
References
The deformation potential of a particular band i induced by a certain phonon mode α through electron-phonon interaction is given by , where ΔVi is the energy change of band i relative to that in the equilibrium structure, l0 is the lattice constant of the equilibrium structure, and Δlα is the lattice constant change due to a structural perturbation from phonon mode α. The calculation is carried out by first displacing the atomic coordinates in the optimized cell from their equilibrium positions by a small amount through following the eigenvector of a certain phonon mode. The band-structure calculation is then performed on a series of such deformed structures with different Δlα (–0.01l0 to 0.01l0). The deformation potential for the bandgap is thus obtained by a linear fit of ΔVbg versus Δlα/l0. The first-principles calculation details were described in Ref. 31.
