Morphology and composition of highly strained InGaAs and InGaAsN layers grown on GaAs substrate

摘要

We have studied the morphology and the composition of highly strained InGaAs and InGaAsN quantum wells (QWs) by transmission electron microscopy. 002 dark-field images show that two symmetrical interfacial layers of about 1.5 nm border the QWs. The selected-area electron diffraction technique gives further evidence of these layers since two extra spots are always observed near the high-index spots on the diffraction patterns. From the position of these extra spots, we determine the strain of the interfacial layers as well as the strain of the middle part of the wells. The comparison of InGaAs and InGaAsN reveals that the morphology of the quaternary alloy QWs is deteriorated and its lateral fluctuation of composition is increased.