EPR spectrum of donors in 6H SiC in a broad temperature range

An EPR study of donors in 6H SiC crystals with an uncompensated donor concentration (ND−NA) of 2×1018 to 1×1016 cm−3 performed in the temperature range 4.2 to 160 K at frequencies of 9 and 140 GHz showed that 6Hn-SiC samples have two donor states in the gap. One of them originates from nitrogen occupying three inequivalent lattice sites with ionization energies of 150 and 80 meV, and the second is connected with a structural defect lying deeper in the gap than nitrogen. The temperature dependences of donor EPR line intensities have been found to deviate from the Curie law. The observed EPR line-intensity peaks of donors are produced in a temperature-driven successive redistribution of donor electrons between the donor levels. The temperature dependences of EPR line intensities obtained from samples with low donor concentrations were used to determine the valley-orbit splitting of nitrogen in cubic sites.