Fachbereich 11 - Physik
Institut für Materialphysik
Diffusion and Defects in Elementary and Compound Semiconductors

Solute and self-diffusion in epilayers and
isotope heterostructures of silicon carbide (SiC)

Diffusion experiments of boron in SiC were performed with boron implanted in 10 µm thick SiC epitaxial layers grown on SiC bulk material. Silicon diffusion was studied utilising isotopically controlled SiC samples which consist of a highly enriched 10 µm thick ²⁸SiC layer grown on top of a natural SiC wafer. Diffusion anneals were carried out in a specially designed high-temperature furnace at temperatures between 1700 °C and 2100 °C. After diffusion, boron and silicon profiles were measured by means of secondary ion mass spectroscopy. Experimental boron diffusion profiles provide strong evidence that boron diffuses via a kick-out mechanism. In this model a boron interstitial occupies a silicon lattice site thereby creating a silicon self-interstitial. Fitting of the experimental profiles yields values for the boron interstitial controlled diffusion coefficient which are consistent with similar results given in the literature. In addition, the analysis yields information about the contribution of silicon self-interstitials to silicon diffusion in SiC. We found that this individual contribution is several orders of magnitude smaller than data for silicon diffusion in SiC reported in the literature. Since this difference is at variance with the observation that the kick-out mechanism dominates boron diffusion in SiC we performed experiments on ³⁰Si diffusion in ²⁸SiC isotope samples. These experiments clearly demonstrate that silicon diffusion in SiC is actually several orders of magnitude slower than the literature data. The new results for silicon diffusion in SiC are consistent with the self-interstitial contribution to silicon diffusion deduced from boron diffusion. This not only supports the kick-out mechanism for boron diffusion in SiC but also indicates that silicon diffusion in SiC is mainly mediated by silicon self-interstitials.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft

Beteiligte Wissenschaftler:

HDoz. Dr. H. Bracht (project leader), Dr. G. Brandes (ATMI, Danbury, Connecticut, USA), Dipl. Phys. M. Laube (Institut für Angewandte Physik, Universität Erlangen-Nürnberg), Dr. G. Pensl (Institut für Angewandte Physik, Universität Erlangen-Nürnberg), PD. Dr. N.A. Stolwijk (project leader)

Veröffentlichungen:

H. Bracht, N.A. Stolwijk, M. Laube, and G. Pensl: Modelling of boron diffusion in silicon carbide, Materials Science Forum 353-356 (2001) 327-330.

K. Rüschenschmidt, H. Bracht, M. Laube, N.A. Stolwijk, and G. Pensl, Diffusion of boron in silicon carbide, Physics B 308-310 (2001) 734-737.

H. Bracht, M. Laube, K. Rüschenschmidt, N.A. Stolwijk, und G. Pensl: Diffusion von Bor in Siliciumkarbid, Verhandl. DPG (VI) 36 (2001) 198.

M. Laube, G. Pensl, H. Bracht, und N.A. Stolwijk: Einfluß einer Si/B- bzw. Ne/B-Coimplantation auf die Bordiffusion in 6H-SiC, Verhandl. DPG (VI) 36 (2001) 198.