  By systematically comparing experimental and theoretical transport
properties, we identify the polar optical phonon scattering as the dominant
mechanism limiting electron mobility in beta-Ga2O3 to lower than 200 cm2/Vs at
300 K for donor doping densities lower than 1018 cm-3. In spite of similar
electron effective mass of beta-Ga2O3 to GaN, the electron mobility is 10x
lower because of a massive Frohlich 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 beta-Ga2O3 that should help calibrate its potential in
high performance device design and applications.
