Abstract
We review in detail the few (simple) theoretical equations that rule all near-equilibrium recombination processes in semiconductors with direct or indirect bandgaps. In the case of 4H-SiC, we discuss their physical significance and show the corresponding limits. Next, we discuss the effect of residual doping in 3C-SiC and show that, from typical low-temperature photoluminescence (LTPL) data, very simple estimates of the doping level can be made. Finally, we focus on aluminum doping in 4H-SiC. Performing a systematic comparison of LTPL spectra with secondary ion mass spectroscopy (SIMS) and/or capacitance-voltage measurements, we show that a reasonably good value of the residual (or intentional) doping level can be obtained from simple optical measurements. An interesting point is that, in many cases, the use of such optical techniques offers the non-negligible advantage to allow detection beyond the SIMS limit.