The characterization of InN growth under high-pressure CVD conditions

Gaining insight into the gas phase and surface chemistry processes that govern the growth of InN and indium-rich group III-nitrides alloys is of crucial importance for understanding and controlling their materials properties. High-pressure chemical vapor deposition (HPCVD) has been shown to be a valuable method for achieving this goal. First results show that InN layers can be grown under HPCVD conditions at 850-900 degrees C in the laminar flow regime of the HPCVD reactor at pressures around 15 bar and ammonia to TMI precursor flow ratio below 200. This is a major step towards the growth of indium rich group Ill-nitride heterostructures due to the close processing windows. The ex situ InN layers analysis shows that the absorption edge in the InN depends strongly on the precursor flow ratio, indicating that the debated InN properties are strongly influenced by the indium-to-nitrogen stoichiometry. By controlling the InN point defect chemistry we showed that the absorption edge shifts from 1.8 eV down to 0.7 eV. The results show a close relation between absorption edge shift in InN and In-N stoichiometry. In order to study the growth under high-pressure CVD conditions, real-time optical characterization techniques have been developed and applied to analyze gas phase constituents as well as the film nucleation and steady state growth at elevated pressures. Principal angle reflection and laser light scattering are employed to study surface chemistry processes at a sub-monolayer level, showing their superiority in optimizing and controlling the growth process. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.