EXAFS study of GaN/AlN multiple quantum wells grown by ammonia MBE

Abstract

AbstractExtended X‐ray absorption fine structure above the Ga–K edge has been used to study the local structure of heterointerfaces in GaN/AlN multiple quantum wells (MQWs) grown by ammonia molecular beam epitaxy. The thickness of AlN and GaN layers in MQWs were evaluated using transmission electron microscopy, X‐ray diffraction and Raman spectroscopy. Two sets of MQWs structures with the number of period about of 20 and more than 100 were studied. The Ga‐Ga interatomic distance in MQWs is lower than that in bulk GaN due to elastic compression of GaN layers in MQWs. This effect is less pronounced in thick structures because of almost full relaxation of GaN layers. The Ga‐Al interatomic distance in thick MQWs is too long, about 0.1 Å, longer than typical values for AlGaN alloys. Then number of Ga cations in the second coordination shell of Ga atoms is lower than that predicted for abrupt heterointerfaces that evidences intermixing of heterointerfaces. The intermixing degree depends on the total thickness of MQWs (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)