Midgap levels in both n- and p-type 4H–SiC epilayers investigated by deep level transient spectroscopy

Abstract

Midgap levels in n- and p-type 4H–SiC epilayers have been investigated by deep level transient spectroscopy (DLTS). The EH6∕7 center (Ec−1.55eV) is the dominant midgap level as observed in DLTS spectra for n-type epilayers. The activation energy of EH6∕7 center is unchanged regardless of applied electric field, indicating that the charge state of the EH6∕7 center may be neutral after electron emission [acceptor-like (0∕−) trap]. In p-type epilayers, a deep level located at 1.49eV above the valence band edge has been detected. The lack of Poole–Frenkel effect in emission time constant from this deep level suggests that this level is donor-like (+∕0). From the energy level and charge state, this defect center may originate from a single carbon vacancy (VC), which has been extensively studied by electron paramagnetic resonance.