Growth Pressure Controlled Nucleation Epitaxy of Pure Phase ε- and β-Ga2O3 Films on Al2O3 via Metal–Organic Chemical Vapor Deposition (original) (raw)

Pure εand β-phase gallium oxide (Ga 2 O 3) films has been successfully grown on Al 2 O 3 (001) substrate via metal-organic chemical vapor deposition (MOCVD) at growth temperature of 500 ℃. Growth pressure controlled nucleation is dominant controlling parameter for pure phase Ga 2 O 3 film growth. Due to the biaxial stress induced by lattice mismatch, hetero-epitaxial ε-phase Ga 2 O 3 is grown on Al 2 O 3 by heterogeneous nucleation at low pressure. However, film growth is dominated by spherical nuclei homogeneous nucleation at pressure higher than 100 mbar, and β-phase Ga 2 O 3 film is grown with mosaic surface. The optimum pressure for the growth of pure ε-Ga 2 O 3 films with superior crystallinity is 35 mbar whereas; the pressure window for pure β-Ga 2 O 3 growth is between 100 mbar to 400 mbar. The growth rate of β-Ga 2 O 3 film is much lower than ε-Ga 2 O 3 film at high pressure. On the other, all Ga 2 O 3 films have showed good optical properties with a band gap of about 4.9 eV. This fundamental research will succor to understand the mechanism of MOCVD growth involving high quality and pure phase εand β-Ga 2 O 3 film.