Growth and optical properties of epitaxial GaN films on Si(1 1 1) using single gas-source molecular beam epitaxy

A novel single-source precursor with composition D₂GaN₃ is used to grow GaN films on Si(111) substrates via AlN buffer layers by gas-source molecular beam epitaxy. The morphological and optical properties of the films are determined as a function of the reaction conditions including deposition temperature. Monocrystalline GaN nanopillars with faceted terminations are readily formed at unusually low temperatures of 275-300 °C from the thermodynamically driven decomposition of the precursor via elimination of D₂ and N₂. Highly oriented layers with columnar morphology and wurtzite microstructure are obtained between 450-750 °C via basal plane growth. The photoluminescence and cathodoluminescence spectra of these materials display strong band edge emission peaks at 360 nm, and in some cases they show broad and weak luminescence features in the range of 530-550 nm. Depositions of D₂GaN₃ in the presence of atomic nitrogen at 650 °C yield epitaxial films that display cubic and hexagonal structures, smooth and continuous surface morphology and distinctive band edge luminescence. Our newly developed process represents one of the simplest methods of GaN growth. Other important advantages include the significant room temperature vapor pressure of the precursor that allows rapid mass transport, which is highly compatible with MBE growth, and the facile decomposition pathway via stoichiometric elimination of benign D₂ and N₂ byproducts yielding highly crystalline GaN materials with unique nano-morphology at low temperatures. This new single source method offers an alternative approach to GaN growth at MBE conditions.