Electronic transitions of the phosphorus-donor in 4H-and 6H-silicon carbide investigated by FTIR-transmission spectroscopy

We have irradiated 4H- and 6H-silicon carbide (SiC) samples with neutrons with an energy distribution of a nuclear 3 reactor. In this way we generated a phosphorus doping of similar to4 x 10(15) cm(-3). We chose 40 and 50 mum thick epitaxial layers with a nitrogen doping of 7 x 10(14) cm(-3) on substrates with similar to10(18) cm(-3) of nitrogen. The substrates of these samples were sucessively removed by mechanical polishing and reactive ion etching. Afterwards the samples were characterized by IR-transmission. In this way we could distinguish between nitrogen- and phosphorus-related absorption. So we could assign in 4H- and in 6H-SiC several absorption lines to electronic transitions of the phosphorus donor. (C) 2002 Elsevier Science B.V. All rights reserved.