Comparison of tunneling current assisted by neutral and positive traps with finite ranged core-potential

Trap assisted tunneling current (JTAT) has been computed for neutral and positive traps with finite ranged core-potential in a metal-oxide-semiconductor structure. The calculation is based on Bardeen transfer Hamiltonian approach and the elastic tunneling approximation and includes both direct tunneling at low voltage and tunneling ionization at high voltage. In both regimes, two different forms of transition matrix elements have been presented and their numerical values have been compared. For both kinds of traps, JTAT shows a similar shape for its dependence on the oxide voltage and increases slightly with increasing the radius of the core-potential. However, compared to the neutral traps, JTAT induced by positive traps is enhanced by about half order due to the existence of the long-ranged Coulomb potential tail. The usual δ-function approximation for the core potential of neutral traps underestimates JTAT by a half order.