Nucleation and growth of InN by high-pressure chemical vapor deposition: Optical monitoring

Abstract

The growth of high quality, stoichiometric InN presents a challenge because of the volatility of atomic nitrogen. To overcome the associated difficulties, a high-pressure chemical vapor deposition (HPCVD) system has been developed, which has opened the avenue for achieving stoichiometric single-phase surface compositions for materials such as InN for which thermal decomposition pressures are large at optimum processing temperatures. We report results obtained during InN growth in the pressure range of 2–15bar to achieve the earlier objectives and to obtain insights into the InN nucleation and growth process. Using real-time optical ultraviolet absorption spectroscopy, we characterized the chemistry of the gas-phase precursors as functions of flow, pressure, and temperature. Highly surface sensitive probing on InN nucleation and steady state growth is achieved by principal-angle-reflectance spectroscopy, allowing the characterization of surface chemistry at a submonolayer level. The InN layers grown at lower temperatures exhibit an absorption edge at 1.85eV, which is shifted towards lower energies as the growth temperatures increase. Absorption edges as low as 0.7eV are observed, values reported for molecular beam epitaxy-grown InN material. The real-time optical monitoring techniques employed demonstrated their superiority in optimizing and controlling the growth process, as well as in gaining insight in gas phase and surface chemistry processes during HPCVD.