Micro-Raman-scattering study of stress distribution in GaN films grown on patterned Si(111) by metal-organic chemical-vapor deposition

GaN films were grown by metal-organic chemical-vapor deposition on Si(111) substrates patterned with arrays of squares and rectangular stripes with a 3.5-μm height and various lateral dimensions. Spatial distributions of tensile stress in the GaN pattern units were mapped out using micro-Raman spectroscopy. At the center of a square GaN film, the tensile stress is the largest and relaxes symmetrically towards the square edges where stress-release free facets are available. The largest crack-free square size for a 1-μm-thick GaN film is in the order of ∼100×100μm2, which is much larger than a theoretically predicted value (∼14μm).