A reduction of edge dislocations in the GaN layer on Si substrate by almost an order of magnitude to 8.0 x 107/cm2 and reduction in screw dislocations by a factor greater than 4 were achieved for the film grown on the Si (111) substrate engineered to have a polycrystalline defective layer at the AlN/Si interface. The formation of a polycrystalline defective layer at the AlN/Si interface by N+ ion implantation provided substrate conditions that result in a hetero-epitaxial GaN film with much improved surface morphology and better crystal quality as compared to the film grown directly on AlN/Si. A mechanism of dislocation defect reduction in the epitaxial film was given based on the detailed study of AlN/Si interfaces as well as the evolution of the AlN buffer layer in the context of this substrate engineering technique, which shows partial decoupling of the III-nitride layers from the substrate to be responsible for the improved characteristics.

Mechanism of Large Area Dislocation Defect Reduction in GaN Layers on AlN/Si (111) by Substrate Engineering. M.Jamil, J.R.Grandusky, V.Jindal, N.Tripathi, F.Shahedipour-Sandvik: Journal of Applied Physics, 2007, 102[2], 023701