Dependence of the V/III Ratio on Indium Incorporation in InGaN Films Grown by Metalorganic Vapour Phase Epitaxy

InGaN epitaxial layers were grown on c-plane sapphire substrates using the metalorganic vapour phase epitaxy (MOVPE) system at 760 °C. By varying the total flow rate of group-III sources (TMI+TEG) with a fixed molar ratio of group-III sources [TMI/(TMI+TEG)], the influence of V/III ratio were investigated from 4500 to 20000. The grown N-polar InGaN layers were investigated by atomic force microscopy and it is found that the surface roughness decreases with increasing the V/III ratios. High resolution X-ray diffraction analyses show that the phase separation decreases with increasing the V/III ratios. Photoluminescence measurements reveal that the peak position of the band-edge emission shifted toward the shorter wavelength with increasing the V/III ratios. Reciprocal space mapping (RSM) analyses were carried out on InGaN films. At low V/III ratio, the phase separation can be detected in InGaN films.