High temperature annealing of Er implanted GaN

Defect recovery, optical activation and diffusion of Er implanted GaN epila yers grown on sapphire were studied after annealing at 1000 degreesC with p roximity cap and 1200 degreesC under nitrogen atmosphere at high pressure ( 1GPa), The erbium ions with 160 keV were implanted at room temperature to n ominal fluences of 5 x 10(14) cm(-2) and 5 x 10(15) cm(-2). Some samples we re co-implanted with oxygen ions to study its influence on the Er behaviour . During implantation a large fraction of Er is incorporated in Ga sites of the GaN lattice for the samples implanted with lower dose. The implantatio n damage recovers almost completely after rapid thermal annealing (120 s) a t 1000 degreesC with proximity cap. The annealing has no influence on the E r profile. The increase of the annealing time leads to the degradation of t he surface due to nitrogen loss. The samples implanted with higher fluence and exposed to the same annealing procedure display distinct behaviour depe nding on the presence of oxygen. In samples without oxygen, the recovery is faster and accompanied by the segregation of Er towards the surface. For s amples containing oxygen the damage recovery proceeds slowly and the Er pro file remains stable. Annealing at 1200 degreesC in nitrogen atmosphere at a pressure of 1GPa promotes the complete recovery of the damage in the sampl e without oxygen. During this annealing, a fraction of Er diffuses into the bulk. After annealing the optical spectra reveal the presence of several s harp lines the intensity of which increases significantly with the annihila tion of the implantation damage. (C) 2001 Elsevier Science B.V. All rights reserved.