On the role of boron in the luminescence of silicon carbide doped with nitrogen and boron

The room temperature photoluminescence of silicon carbide doped with nitrogen and boron is investigated. A comparison is made of the photoluminescence efficiency of 6 H SiC samples prepared in three different ways. Some results obtained on 411 samples are also presented. For samples doped with boron during crystal growth a reasonable efficiency is only obtainable when the boron concentration is high. Boron diffusion into n-type samples or neutron irradiation and subsequent annealing of n-type samples containing boron led for relatively low boron concentrations to high efficiencies. From the results it is concluded that a boron centre different from the boron acceptor known from electrical transport studies is involved. Results obtained recently on donor–acceptor pair spectra support this conclusion and indicate that the boron centre required for luminescence is a boron atom on a carbon site, implying that the boron acceptor mentioned earlier may be a boron atom on a silicon site or a more complex centre.