Analysis of growth rate and crystal quality of AlN epilayers by flow-modulated metal organic chemical vapor deposition

AlN templates have been grown on sapphire by flow-modulated metal organic chemical vapor deposition (MOCVD). By analyzing the TMAl duty ratio R, TMAl utilization ratio β and parasitic reaction ratio α, we obtained the quantitative relationship between flow-modulated modes and growth rate, and then proposed two kinds of flow-modulated modes to increase the growth rate of AlN. Besides, we found the continuous growth in flow-modulated mode can transform the AlN growth mode from the step-bunching growth into the two-dimension growth and accordingly improve the crystal quality of AlN. Finally, the AlN template with a relatively fast growth rate (0.98 μm/h) and flat surface morphology (RMS = 0.5 nm) was obtained by NH3 pulse-flow mode with a small duty ratio of NH3.