High-temperature photoluminescence spectroscopy in p-type SiC

Abstract

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 °C (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.