Spectro-microscopy of Si doped GaN films

The surface segregation of Si used for doping of GaN films grown by metal-organic vapor phase epitaxy has been detected by spectro-microscopy. Facetted cracks with a threefold symmetry have been observed which extend over several micrometers. From local spectra, an enhanced Si segregation is deduced at the facets as compared to the flat surface. A scheme is presented which allows to extract quantitative information about the local surface concentrations for such facetted surface systems. Following to this scheme, Si coverages as high as approximately 4.5 × 1014 Si atoms/cm2 occur at the facets which clearly proves the segregation tendency of Si.