Photoluminescence Due to Al, Ga, and B Acceptors in 4H‐, 6H‐, and 3 C ‐ SiC Grown from a Si Melt

Single crystals of 4H‐, 6H‐, and have been grown from a silicon melt in a graphite crucible. Visible photoluminescences due to Al, Ga, and B acceptors in these crystals are studied in the temperature range from 2° to 450°K. The luminescence color varies from violet to near‐infrared depending on the energy level of the acceptor and the energy gap of the polytype. All the luminescences at low temperatures are thought to be due to pair recombination between the N donor introduced unintentionally and the Al, Ga, or B acceptor. Each spectrum consists of a zero‐phonon peak and its phonon replicas. At higher temperatures, another emission appears owing to the recombination of free electrons with bound holes at the acceptors. From the luminescence spectra and the thermal quenching of the emission intensity, the ionization energy of Ga is found to be a little larger than that of Al, while B has much larger ionization energy. The values obtained for are , , and for Al, Ga, and B, respectively, where is the exciton binding energy of the order of 10 meV. Owing to the deep level of the B acceptor, the luminescence has a different spectrum from those due to Al and Ga, and is intense even at room temperature.