Impact of the dangling bond defects and grain boundaries on trapping recombination process in polycrystalline 3C SiC

Abstract The bulk polycrystalline (pc) 3C SiC of n- and p-type obtained by thermal decomposition of methyltrichlorosilane vapor have been studied by applying the electron paramagnetic resonance (EPR), direct current (DC) conductivity, photoconductivity (PC) and PC time-resolved decay methods. The energy level of the two donor-like minority carrier traps at e1 = 77 meV and e2 = 92.6 meV located at the grain boundaries (GB) of pc-3C SiC has been obtained using the measurements of the temperature dependence of DC conductivity and PC in the range of 80–600 K. The minority carrier traps assigned to carbon and silicon dangling bonds with the carbon back bonds were observed in the EPR spectra of pc-3C SiC of n- and p-type at g = 2.0029(3), g = 20042(3), respectively. The PC time decay after the termination of the photo-excitation was studied in monocrystalline and pc-3C SiC of n- and p-type at 80 K. The persistent relaxation of PC has been described by kinetic equations accounting the trapping, ionization, and recombination processes of non-equilibrium charge carriers bound dynamically to shallow donors and acceptors. We have concluded that the main process responsible for the long-lived relaxation of the PC is trap-assisted electron-hole recombination in n-type pc-3C SiC and ionization of boron acceptors, as well as the hole escape/capture at the boron level in p-type pc-3C SiC. The differences in the relaxation process of the PC in n- and p-type pc-3C SiC were explained by the presence of the potential barrier height of about 8.6 meV at GB for the capture of the majority carriers in p-type pc-3C SiC.