Evolution of surface morphology and film stress during MOCVD growth of InN on sapphire substrates

The evolution of surface morphology and film stress during metalorganic chemical vapor deposition (MOCVD) growth of InN on sapphire substrates was investigated. In situ stress measurements were carried out using a multi-beam optical stress sensor system, which measures changes in sample curvature during film deposition. Growth of InN on a low temperature AlN buffer layer on sapphire was observed to occur via island nucleation and coalescence. A constant tensile growth stress of approximately 0.2GPa was measured in the InN films for thickness < 200nm. For films thicker than approximately 200nm, growth continued at almost zero stress. This corresponded to the point at which film delamination was observed to occur at growth temperature. This undesirable stress relief mechanism limits the thickness of InN layers that were grown by MOCVD on sapphire using an AlN buffer layer.