Oxygen in silicon carbide: shallow donors and deep accepters

The electrical and optical properties of oxygen (O)-implanted 6H-silicon carbide (SiC) chemical vapor deposition (CVD) epilayers are investigated by Hall effect, admittance spectroscopy, deep level transient spectroscopy (DLTS) and low temperature photoluminescence (LTPL). Two types of O-related centers are found: shallow donors in the energy range of (129-360) meV below the conduction band edge as well as deep acceptor-like defects at E-C - 480 meV, E-C - 560 meV and E-C - 610 meV. For the shallow donors, a certain sensitivity to heat treatments is demonstrated in terms of a decrease of their ionization energies when exposing the O+-implanted epilayers to temperatures at 1650-1800 degrees C. In addition, evidence has been found for the incorporation of O in as-grown 4H-SiC CVD epilayers indicated by the observation of deep O-related defect centers in DLTS spectra. (C) 1999 Elsevier Science S.A. All rights reserved.