The morphology and density of InGaN nanoislands can be controlled by the choice of proper growth conditions for metal organic vapor phase epitaxy. Scanning tunneling microscopy has been used to investigate the dependence of InGaN island morphology on the growth parameters. A heterogeneous nucleation of large InGaN islands with a complex structure is observed after growth at 650 degrees C in conjunction with a high In partial pressure. For 600 degrees C and low In partial pressure, however, the homogeneous nucleation of small islands of sizes suitable for three-dimensional quantum confinement is found, with very high densities of 10(12) cm(-2). The influence of the growth temperature and the In partial pressure is discussed in terms of thermally activated diffusion and surface mobility. (c) 2007 American Vacuum Society.