The growth of hexagonal AlN directly onto (111)Si was studied, as a function of the film thickness, by means of grazing incidence X-ray diffractometry and high-resolution electron microscopy. Two epitaxial relationships were observed. One was (00•1)[2¯1•0]AlN||(111)[02¯2]Si, which predominated at deposition temperatures greater than 650C, and (00•1)[10•0]AlN||(111)[02¯2]Si. The average in-plane crystallite size was 16.2nm for a 4nm-thick layer, the in-plane rotation was about 2º, and the dislocations introduced an average strain distribution of 0.8%. The Si/AlN interface was very sharp, and complete relaxation (down to about 0.2%) occurred within one bilayer. No long-range order was observed at the interface; thus implying a low mobility of AlN species, on Si, which inhibited any structural rearrangement. The in-plane rotations originated from early stages in the layer growth, and decreased with layer thickness; especially for thicknesses greater than 25nm.

A.Bourret, A.Barski, J.L.Rouvière, G.Renaud, A.Barbier: Journal of Applied Physics, 1998, 83[4], 2003-9