Silicon implantation in epitaxial GaN layers: Encapsulant annealing and electrical properties

Silicon ions have been implanted into GaN layers epitaxially grown on an AlN/(0001)-Al2O3 substrate to a dose of 1x10(15)/cm(2). The Si-implanted GaN has been rapid thermal annealed at temperatures between 800 and 1250degreesC. Thermal pits are formed in the surface during annealing at 1200degreesC, resulting in deterioration of the morphology. The surface deterioration is effectively suppressed by using a 140-nm-thick Si3N4 film as an encapsulant during annealing up to 1250degreesC. The electrical activation process for Si atoms has an activation energy of 3.1 eV in the range of 1000 to 1250degreesC. Carrier concentration and mobility profiles for n-type layers formed by Si implantation have been examined by differential Hall-effect measurements. A very high electrical activity for implanted Si atoms of 86% can be achieved, and a highly doped n-type layer with a peak carrier concentration of 6x10(19)/cm(3) is formed after annealing at 1250degreesC. Electrons generated from Si atoms located near the end of range are trapped by defects remaining after annealing at 1250degreesC. (C) 2004 American Institute of Physics.