1. A. Schöner, N. Nordell, K. Rottner, R. Helbig and G. Pensl, Silicon Carbide and Related Materials 1995 (Bristol, U.K.: Institute of Phys., 1996), p. 493.
2. W. Suttrop, G. Pensl and P. Lanig, Appl. Phys. A 51, 231 (1990).
3. M. Ghezzo, D.M. Brown, E. Downey, J. Kretchmer and J.J. Kopanski, Appl. Phys. Lett. 63, 1206 (1993).
4. M.V. Rao, P. Griffiths, O.W. Holland, G. Kelner, J.A. Freitas, Jr., D.S. Simons, P.H. Chi and M. Ghezzo, J. Appl. Phys. 77, 2479 (1995).
5. G. Pensl, V.V. Afanas’ev, M. Bassler, M. Schadt, T. Troffer, J. Heindl, H.P. Strunk, M. Maier and W.J. Choyke, Silicon Carbide and Related Materials 1995 (Bristol, U.K.: Institute of Phys., 1996), p. 275.