In distribution in InGaN quantum wells: influence of phase separation, In segregation and In desorption

The local In distribution in InGaN quantum wells was measured in samples which were grown by metalorganic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) varying systematically the metal-flux ratio and the growth rate. The composition analyses were performed by local lattice parameter measurements based on lattice-fringe transmission electron microscopy (TEM) images. Composition fluctuations are observed in all samples on two typical scales: In-rich clusters with lateral sizes below 5 nm with high In concentration and weaker composition fluctuations on a 100 nm scale. The size of the clusters does not depend on the growth conditions, but the amplitude of the composition fluctuations is influenced by the growth rate. In-concentration profiles along the growth direction show the effect of In desorption and In segregation during the growth.