DONORS IN CUBIC SILICON-CARBIDE

Clearly resolved donor excitation spectra in cubic (3C) silicon carbid e have been studied in infrared transmission as a function of temperat ure and applied magnetic field. Accurate positions for excited states of nitrogen on the carbon site have been determined and are in excelle nt agreement with effective mass theory using values for longitudinal and transverse effective masses from cyclotron resonance results. Phot oluminescence spectra in the two-electron satellite region are consist ent with the transmission results and give the nitrogen 2s state bindi ng energy. Two other donors are observed with low concentrations: an e ffective mass donor at 47.7 meV and avery shallow donor with a binding energy of 34 meV. Zeeman splitting of the 2p(+/-) excited states with B parallel to[111] for all three donors is in good agreement with the previously measured transverse effective mass. Valley-orbit splitting of the nitrogen ground state is observed but no valley-orbit splittin g can be seen for the effective mass donor as expected. We suggest tha t the very shallow donor has a repulsive core (negative chemical shift ) and inverted ordering with the Is(A(1)) ground state above the 1s(E) ground state similar to lithium in silicon.