Mist-chemical vapor deposition grown Ge-doped α-Ga2O3 thin films with high electron mobility

Unintentionally doped and Ge-doped α-Ga2O3 films were grown on m-plane sapphire substrates via mist-chemical vapor deposition at a substrate temperature of 600 °C and a growth rate of 3.3 μm/h. Hall-effect measurements at room temperature indicated that the unintentionally doped film exhibited a low carrier concentration of 3 × 1016 cm−3, and the highest electron mobility reached 99 cm2 V−1 s−1 for the Ge-doped α-Ga2O3 film with a carrier concentration of 5.8 × 1017 cm−3. Temperature-dependent Hall-effect measurements clarified the transport mechanism: scattering caused by dislocations and ionized impurities dominate at low temperatures in films with carrier concentrations of 1.7 × 1017 and 5.8 × 1017 cm−3, respectively, whereas polar optical phonons are the main origin of electron scattering around room temperature. The average densities of threading screw and edge dislocations in Ge-doped films prepared herein are 6.0 × 108 and 1.1 × 109 cm−2, respectively, which are lower than those for α-Ga2O3 films grown on sapphire substrates to date. The low carrier concentration and high electron mobility achieved by reducing the dislocation density suggest the promising application potential of α-Ga2O3 in power electronics and high-frequency devices.