Epitaxial growth of aluminum nitride on AlGaN by reactive sputteringat low temperature

We report the synthesis of 1 μ m thick single crystalline aluminum nitride films by dc magnetron sputtering on Al Ga N ∕ Ga N layer grown on sapphire substrate at low temperature (substrate temperature < 250 ° C ). The microstructure of c -axis oriented AlN films deposited on Si (100) and AlGaN ⟨0001⟩ substrates was studied by x-ray diffraction, selected area electron diffraction, and transmission electron microscopy. The optimization of process parameters, involving low energetic ion bombardment on film surface ( 20 - 30 eV ) during the growth, leads to an increase in the surface mobility and thus promotes AlN epitaxial growth on AlGaN substrate at 250 ° C .