Determination of ionization energies of the nitrogen donors in 6H-SiC by admittance spectroscopy

The nitrogen donor levels have been studied by admittance spectroscopy between 20 and 200 K in Schottky barriers made on lightly n-type epitaxial 6H-SiC layers. Measurements at different frequencies yield different freezeout temperatures which in turn are used to determine the donor level energies. Two electron traps at E_c-0.082 eV and at E_c-0.140 eV were detected. These levels are associated with nitrogen, respectively, at the hexagonal sites for the former and at the cubic sites for the latter level.