Depth profiles of electron and hole traps generated by reactive ion etching near the surface of 4H-SiC

Deep levels in the whole bandgap of 4H-SiC generated by reactive ion etching (RIE) are investigated with both n- and p-type SiC Schottky barrier diodes by deep-level transient spectroscopy (DLTS). Depth profiles of the observed deep levels were analyzed using the DLTS peak intensities at various bias voltages and numerical calculations. The major electron traps detected after RIE and subsequent annealing at 1300 °C include the Z1/2 (EC−0.66 eV), ON1 (EC−0.88 eV), ON2 (EC−0.95 eV), and EH6/7 (EC−1.50 eV) centers, and the major hole traps include the UK1 (EV+0.51 eV), UK2 (EV+0.72 eV), HK0 (EV+0.77 eV), HK2 (EV+0.79 eV), and HK3 (EV+1.31 eV) centers, where EC and EV denote the conduction and valence band edges, respectively. Most of the traps were localized near the surface (<0.5 μm) with a maximum density of about 1×1015 cm−3, but several traps such as the ON1 and HK0 centers penetrate deep into the bulk region (>2 μm). By annealing at 1400 °C, most of the hole traps were eliminated, but several electron traps remained. From these results, the origins of these defects are discussed.