Decomposition in as-grown (Ga,In)(N,As) quantum wells

We report on the investigation of the local element distribution in as-grown (Ga,In)(N,As) quantum wells with high In and N contents by using low-loss electron energy-loss spectroscopy combined with dark-field transmission electron microscopy. The (Ga,In)(N,As) quantum wells were grown on GaAs(001) substrates at different growth temperatures by molecular-beam epitaxy. Lateral modulations on the nanometer scale were detected with reversal In and N distributions pointing to the existence of regions with a more favorable Ga–N and In–As bond configurations, respectively. These composition fluctuations are the driving force for the morphological instabilities at the interfaces. Lowering the growth temperature of the quantum well results in a more homogeneous element distribution of the quaternary compound. This result is discussed with regard to the influence of the epitaxial strain and cohesive bond energy on the alloy formation during epitaxial growth.