PNNL

Abstract

This work aims to investigate the formation and structure-phase-morphology correlation of GaON thin films by systematically oxidizing GaN on Si substrates. An extensive examination of the nanoscale, crystallographic growth dynamics of the system, which is impacted by the thermal energy given to the GaN, is carried out to derive a deeper understanding of the growth kinetics, morphology and microstructure evolution, and optical properties of GaON films. Thermal annealing of GaN films was performed in the temperature range of 900-1200 oC. Crystal structure, phase formation, chemical composition, surface morphology, and microstructure evolution of GaON films were investigated as a function of temperature. Increasing temperature induces surface oxidation, which results in the formation of stable ß-Ga2O3 phase in the GaN matrix, where the overall film composition evolves from nitride (GaN) to oxynitride (GaON). While GaN surfaces are smooth, planar, and featureless, oxidation induced granular-to-rod shaped morphology evolution is seen with increasing temperature to 1200 oC. The considerable texturing and stability of the nanocrystalline GaON on Si substrates can be attributed to the surface and interface driven modification because of thermal treatment. The structure-phase-chemical composition correlation, which will be useful for nanocrystalline materials for selective optoelectronic applications, is established in GaON films made by thermal treatment of GaN.