Stability of deep centers in 4H-SiC epitaxial layers during thermal annealing

N -type epitaxial 4H-SiC layers grown by hot-wall chemical vapor deposition were investigated with regard to deep centers by capacitance-voltage measurements and deep level transient spectroscopy (DLTS). The DLTS spectra revealed that the concentrations of deep centers were reduced by one order of magnitude by annealing at 1700°C, compared to those in an as-grown material. The Z1∕2 center with an energy level of 0.59±0.03eV and the EH6∕7 center with an energy level of 1.66±0.11eV below the conduction band edge are annealed out at a temperature of 1700°C or higher.