Diffusion of boron in 6H and 4H SiC coimplanted with boron and nitrogen ions

The diffusion behavior of boron (B) and nitrogen (N) implanted in 6H and 4H silicon carbide (SiC) samples was investigated using secondary ion mass spectroscopy. The samples were either coimplanted with B and N ions or implanted with each element alone. The annealing was performed at 1700 degreesC for times ranging from 10 to 1800 s in argon ambient or in the vapors of silicon and carbon. Transmission electron microscopy has been used to determine the structural properties of implanted layers after the annealing. The N concentration profiles remained unchanged after the annealing. B atoms showed transient enhanced out- and in-diffusion. The coimplantation reduced the fraction of mobile B atoms participating in out- and in-diffusion processes and resulted in an increase in the density and decrease in size of dislocation loops formed in the implanted layer. The B diffusion coefficients in both SiC polytypes have been determined and a diffusion mechanism has been discussed. (C) 2004 American Institute of Physics. (C) 2004 American Institute of Physics.