Capacitance transient study of the metastable M center in n-type 4H-SiC

The metastable M center in n-type 4H silicon carbide is studied in detail after it has been introduced by 2.5 MeV proton irradiation with a fluence of 1x1012 cm-2. The experimental procedures included deep-level transient spectroscopy, carrier capture coefficient and capacitance versus temperature measurements, and pulse-train measurements. The pulse-train measurements are reproduced by simulations. Three band-gap levels have previously been assigned to the M center: M1 at EC-0.42 eV, M2 at EC-0.63 eV, and M3 at EC-0.83 eV, where EC is the conduction-band edge. Direct measurements of the majority-carrier capture cross sections show that the cross section values extracted from Arrhenius plots are about two orders of magnitude too large, indicating a large entropy factor. A detailed configuration diagram of the M center is presented, including charge state levels and reconfiguration barriers. Evidence in support of a fourth M center level, not explicitly observed, is presented. Isochronal and isothermal annealing experiments show that the M center anneal out between 310 and 370 deg. C in a process displaying first-order kinetics. The annealing process, which is shown to have an activation energy of 2.0 eV, is identified as dissociation