High-temperature photoluminescence spectroscopy in p-type SiC

Photoluminescence (PL) spectra were analysed for Al- and B-doped p-type silicon carbide single crystals in a broad spectral range between 0.7 eV and 3.25 eV at temperatures up to 300 degreesC (570 K). Of special interest was to explore the effect of thermal activation of the PL intensity, which is exhibited as a strong increase in the visible luminescence at elevated temperatures. Specifically, the 'orange' PL band, with a maximum at 1.82 eV shows thermal activation exceeding one order of magnitude. Using thermally stimulated luminescence (TSL), we present experimental evidence that the Al and B acceptors in p-type SiC act as hole traps being partially compensated by deep donors. Thermal PL activation allowed for identification of luminescence transition at the 'orange' centres as a free-to-bound hole recombination for both types of impurities. Room temperature spatially resolved PL spectroscopy and TSL imaging on 50 mm. diameter p-type SiC wafers confirmed the mechanism of luminescence, and revealed spatial inhomogeneity of the concentration of the major compensating defects.