Electric field enhancement of electron emission rates from Z1/2 centers in 4H-SiC

Z(1/2) defect centers were produced by irradiating 4H-SiC bulk samples with 1 MeV electrons at room temperature. The emission rate dependence on the electric field in the depletion region was measured using deep level transient spectroscopy and double-correlation deep level transient spectroscopy. It is found that the Z(1/2) defect level shows a strong electric field dependence with activation energy decreasing from E-c-0.72 eV at zero field to E-c-0.47 eV at 6.91 x 10(5) V/cm. The phonon assisted tunneling model of Karpus and Perel [Sov. Phys. JETP 64, 1376 (1986)] completely describes the experimental data. This model describes the dependence of the emission rate on electric field F as e(n)(F) = e(no) exp (F-2/F-c(2)), where F-c is the characteristic field that depends on the phonon assisted tunneling time tau(2). The values of F-c and tau(2) were determined and the analysis of the data leads to the suggestion that Z(1/2) may be a substitutional point defect. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3224872]