EXAFS study of intermixing in GaN/AlN quantum wells

Extended X-ray absorption fine structure above the GaK edge has been used to study the local structure of heterointerfaces in GaN/AlN multiple quantum wells (MQWs) grown with ammonia molecular beam epitaxy at different growth temperatures. Thickness of AlN and GaN layers in MQWs were evaluated using transmission electron microscopy and photoluminescence spectroscopy. The Ga-Ga interatomic distance in MQWs is lower than that in bulk GaN due to elastic compression of GaN layers in MQWs. The number of Ga cations in the second coordination shell of Ga atoms is lower than that predicted for abrupt heterointerfaces that is an evidence for intermixing of heterointerfaces. A degree of intermixing linearly rises with an increase in the growth temperature.