Growth of aluminum nitride on (111) silicon: Microstructure and interface structure

The growth of hexagonal aluminum nitride directly on (111) silicon has been studied by grazing incidence x-ray diffraction and high resolution electron microscopy as a function of film thickness. Two epitaxial relationships were observed: (1) AlN (0001) [2<(11)over bar>0]//Si(111) [02 (2) over bar], which prevails at deposition temperatures larger than 650 degrees C, and (2) AlN (0001) [10 (1) over bar 0]//Si(111) [02 (2) over bar]. For a 40 Angstrom thick layer, the average in-plane crystallite size is 162 Angstrom, the in-plane rotation is similar to 2 degrees and the dislocations induce an average strain distribution of 0.8%. The Si/AlN interface is very sharp and complete relaxation (down to similar to 0.2%) occurs within one bilayer. No long range order was observed at the interface. This implies a low mobility of the AlN species on Si, inhibiting any structural rearrangement. In particular the in-plane rotations originate from the early stage of the layer growth and decrease with the layer thickness, especially for thicknesses larger than 250 Angstrom. (C) 1998 American Institute of Physics.