A method of reducing threading dislocation density in AlN epilayers grown on

sapphire substrate was reported. By introducing an AlN buffer layer grown by a

pulsed atomic-layer epitaxy method, threading dislocations in epitaxial AlN films

were greatly decreased. From transmission electron microscopic images, a clear

sub-interface was observed between the buffer layer and the subsequently

continuous grown AlN epilayer. In the vicinity of the sub-interface, the redirection,

annihilation, and termination of threading dislocations were observed. The increase

in lateral growth rate accounted for threading dislocation redirection and

annihilation in the AlN epilayer. Strain variation between the two regions resulted in the termination of threading dislocations due to dislocation line energy

minimization.

Reduction in Threading Dislocation Densities in AlN Epilayer by Introducing a

Pulsed Atomic-Layer Epitaxial Buffer Layer. L.W.Sang, Z.X.Qin, H.Fang, T.Dai,

Z.J.Yang, B.Shen, G.Y.Zhang, X.P.Zhang, J.Xu, D.P.Yu: Applied Physics Letters,

2008, 93[12], 122104