Crystalline quality of InxAl1-xN with different indium contents around lattice-matched to GaN

200 nm thick In_xAl_1-xN epilayers around lattice-matched to GaN were grown on GaN templates by MOCVD. The elastic strain, surface morphology and crystalline quality of the In_xAl_1-xN were evaluated by high resolution X-ray diffraction (HRXRD) measurements, scanning electron microscopy (SEM) images and Rutherford backscattering spectroscopy (RBS) analyses. The strain effect, as while as the influences of indium and the GaN templates with different dislocation densities on the quality of In_xAl_1-xN epilayers were discussed. It is found that the crystalline quality was quite good when In_xAl_1-xN around lattice matched to GaN and degraded when In_xAl_1-xN under relatively large tensile or compressive strain accompanied by formation of crack or pits of reverse pyramid. The micro-morphology observations of In_xAl_1-xN layers with different indium compositions showed that the formation of dislocations was related with indium and compressive strain in In_xAl_1-xN layers. Furthermore, more pits were observed in lattice matched In_xAl_1-xN layers on GaN template of high dislocation density than samples on GaN template with low dislocation density GaN. It is believed that threading dislocations induced by GaN template might be a part of origin of the pits, and modulate the effect of compressive stain on the In_xAl_1-xN quality.