Heteroepitaxy of ε-Ga2O3 thin films grown on AlN/Si(1 1 1) templates by metal–organic chemical vapor deposition

High quality ε-phase gallium oxide (Ga2O3) thin films grown on Si(1 1 1) substrates by metal–organic chemical vapor deposition (MOCVD) have been demonstrated. It is found that Ga2O3 thin films grown directly on bare silicon substrate possess poor crystal quality and uniformity due to the oxidation on the surface of silicon. Ga2O3 thin films could be successfully grown on silicon substrate only after an AlN layer is inserted. The Ga2O3 samples are grown on AlN/Si by a two-step method and the structural properties is investigated via X-ray diffraction, scanning electron microscope and transmission electron microscope. The growth pressure is found to be an important parameter, which influences the phase-purity and coalescence of the ε- Ga2O3 thin films. Low growth pressure could suppress the appearance of β-Ga2O3 and promote the lateral growth and coalescence of ε-Ga2O3 thin film. By optimizing the growth pressure of nucleation layer and epilayer, pure ε-Ga2O3 thin film with FWHMs of (0 0 4)-plane and (0 1 3)-plane rocking curves of 1.83° and 2.31° are achieved.