Photoluminescence excitation spectroscopy on the donor-acceptor pair luminescence in 4H and 6H SiC

This paper presents the excitation spectra of the donor-acceptor pair emission in 4H and 6H SiC doped with nitrogen and aluminum, obtained using a suitable dye laser. When the excitation spectra of different pairs are compared, two main types of peaks are seen in the spectra: peaks appearing at almost the same energy shift from the registered photon energy, and peaks appearing at constant absolute energy positions. The former are attributed mainly to transitions leaving either the donor electron, or the acceptor hole, or both in excited states, whereas the latter are seen as evidence for extensive exciton transfer from neutral acceptors to donor-acceptor pairs.