A new method for extracting the trap energy in insulators

A simple procedure is reported for extracting the energy of trap levels from the I-V characteristics of insulators at room temperature. It is shown that by plotting ln(JE) vs 1/E it is possible to obtain the trap energy directly from the slope, and an estimate of the trap density from the intercept. Furthermore, it is demonstrated that our simplified, trap-assisted tunneling equation differs from the exact solution by only ∼1%-3% for "typical" nitridation-induced trap energies (2-3 eV), and for fields above 4 MV/cm. At lower trap energies this error is shown to be manifested only in the extracted trap densities and hence the new model can still be used to obtain the trap depth. For nitrided-oxide capacitors it is shown that this nitridation-induced trap energy is ∼2.2 eV which is in good agreement with the work of others. For transistors fabricated on the same wafers evidence is found for a distribution of shallow (≤1 eV) traps which could be due to damage introduced during the source/drain implant.
© 1993 American Institute of Physics