Donors in cubic silicon carbide

Abstract

Clearly resolved donor excitation spectra in cubic (3C) silicon carbide have been studied in infrared transmission as a function of temperature and applied magnetic field. Accurate positions for excited states of nitrogen on the carbon site have been determined and are in excellent agreement with effective mass theory using values for longitudinal and transverse effective masses from cyclotron resonance results. Photoluminescence spectra in the two-electron satellite region are consistent with the transmission results and give the nitrogen 2s state binding energy. Two other donors are observed with low concentrations: an effective mass donor at 47.7 meV and a very shallow donor with a binding energy of 34 meV. Zeeman splitting of the 2p ± excited states with B ∥ [ 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 splitting can be seen for the effective mass donor as expected. We suggest that the very shallow donor has a repulsive core (negative chemical shift) and inverted ordering with the 1s(A 1) ground state above the 1s(E) ground state similar to lithium in silicon.