Electrical conductivity and lattice expansion of β-Ga2O3 below room temperature

The temperature dependence of the electrical properties of $\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3$ is analyzed from liquid helium to room temperature by Hall measurements. Below $100\mathrm{K}$ , the carrier motion takes place within the impurity conduction band and it shows a power-law dependence. An electrostructural coupling is ascertained. Thermal activation in the conduction band is observed above $100\mathrm{K}$ , with an activation energy $E_a=7\mathrm{meV}$ . Thermal conductivity is measured to $13\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ . Further, it is shown that Ti is a good Ohmic electrode for $n$ -type $\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3$ substrates.