Electrical and microstructural properties of highly boron-implantation doped 6H-SiC.

Boron was implanted with four energies and doses at 400 °C into 6H-SiC epilayers to form a 500 nm thick doped layer with a mean concentration between 1x10[sup 18] and 1.5x10[sup 21] cm[sup -3]. Two annealing techniques were used: furnace and flash lamp annealing. The electrical and microstructural effects were investigated using temperature dependent Hall measurements, cross sectional electron microscopy, and secondary ion mass spectrometry. During the annealing two competing processes occurred: boron outdiffusion and growth of boron containing precipitates. The efficiency of these individual processes is different for varying dopant concentrations as well as annealing techniques. After furnace annealing at temperatures between 1550 and 1750 °C and for a mean boron concentration of 5x10[sup 19] cm[sup -3] boron containing clusters are found mainly around the region of the three deeper implantation peaks. In the surface region boron outdiffusion is observed adjusting a concentration of 1.5x10[sup 19] cm[sup -3]. Using flash lamp annealing, the outdiffusion is negligible. For high dopant concentrations (1.5x10[sup 21] cm[sup -3]) the growth of random distributed boron precipitates is the dominating effect independent of the used annealing techniques. The electrical activation is limited due to the solubility of boron in SiC. After furnace annealing Hall effect measurements show a maximum hole concentration of about 2x10[sup 16] cm[sup -3] for the boron concentration of about 5x10[sup 18] cm[sup -3]. Alternative to the furnace annealing, the electrical properties after flash lamp annealing at about 2000 °C, 20 ms show a slight enhancement of the maximum hole concentration for boron concentrations <3x10[sup 20] cm[sup -3]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]