Homoepitaxial growth of Ge doped β-gallium oxide thin films by mist chemical vapor deposition

Abstract This study demonstrated homoepitaxial growth of Ge-doped β-Ga2O3 thin films on β-Ga2O3 substrates via mist chemical vapor deposition (CVD) using GeI4, a water-soluble Ge precursor. The carrier concentration of the Ge-doped β-Ga2O3 thin films was controlled by varying the Ge precursor concentration in the solution. A mobility of 66 cm2V-1s-1 was obtained at a carrier density of 3.4×1018 cm-3 using oxygen gas. X-ray diffraction (XRD) scans revealed that homoepitaxial Ge-doped β-Ga2O3 thin films were grown on β-Ga2O3 without phase separation. However, the XRD rocking curves revealed that the mist CVD- grown Ge-doped β-Ga2O3 was slightly degraded compared to the substrate as the Ge concentration increased. The surface morphologies of the Ge-doped β-Ga2O3 exhibited atomically flat surfaces with a root mean square roughness of less than 1 nm. These results indicate that the Ge-doped β-Ga2O3 thin films prepared by mist chemical vapor deposition are promising for device applications.