Effect of hydrogen flow rate on AlN and AlGaN growth is investigated in AMEC Prism(R) D-Blue MOCVD platform. It is found that AlN growth rate increases with the increase of hydrogen flow rate. Al composition in AlGaN material increases initially with the increase of hydrogen flow rate at relatively low hydrogen flow rates (< 120 slm) and then saturates at high hydrogen flow rates. GaN partial growth rate shows a "U" shaped profile. Computational fluid dynamics (CFD) simulation of AlN growth is performed to understand the growth mechanism. The simulation results indicate that higher hydrogen Flow rate could suppress the parasitic reaction and particle formation during AlN growth. Thus more source gases can be transported to the wafer surface, resulting in the increase of AlN growth rate. (C) 2015 Elsevier B.V. All rights reserved.