Role of strain in growth kinetics of AlGaN layers during plasma-assisted molecular beam epitaxy

Comparative study of growth kinetics of the AlxGa1−xN (x=0-1) layers grown by plasma-assisted molecular beam epitaxy (PA MBE) under different growth conditions (group III to activated nitrogen and Al to Ga flux ratios) is presented. The strong influence of elastic stress on the surface morphology, growth rate and Al content in AlxGa1−xN (x=0-1) layers is most pronounced for the AlxGa1−xN films with high Al-content grown atop of the 2D-AlN buffer layer at near the unity flux ratio FIII/FN∼1. The use of strong Ga-rich growth conditions with FIII/FN∼1.6-2 for the growth of AlxGa1−xN/2D-AlN with high Al-content (x>0.25) allows one to reduce the strain effect as well as provide smooth surface morphology and precise control of Al content in the AlxGa1−xN (x=0-1) layers by employing a simple ratio x=FAl/FN.