Mechanism of large area dislocation defect reduction in GaN layers on AlNSi (111) by substrate engineering

Abstract

A reduction of edge dislocations in the GaN layer on Si substrate by almost an order of magnitude to 8.0× 107 cm2 and reduction in screw dislocations by a factor greater than 4 are achieved for the film grown on the Si (111) substrate engineered to have a polycrystalline defective layer at the AlNSi interface. The formation of a polycrystalline defective layer at the AlNSi interface by N+ ion implantation provides substrate conditions that result in a heteroepitaxial GaN film with much improved surface morphology and better crystal quality as compared to the film grown directly on AlNSi. A mechanism of dislocation defect reduction in the epitaxial film is given based on the detailed study of AlNSi 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. © 2007 American Institute of Physics.