We report on the epitaxial growth of highly conductive degenerated Ge or Si doped β-Ga2O3 and β-(Al x Ga1−x )2O3 films by MOCVD. Highly conductive homoepitaxial β-Ga2O3 layers with record conductivities of 2523 and 1581 S cm−1 were realized using Si and Ge dopants. Highly conductive Si doped β-(Al x Ga1−x )2O3 films were also grown. The incorporation of Si decreased with the increase in Al content and layer thickness. Record high conductivity of 612 S cm−1 was attained for coherently strained β-(Al0.12Ga0.88)2O3.