Density-gradient analysis of MOS tunneling

The density-gradient description of quantum transport is applied to the analysis of tunneling phenomena in ultrathin (<25 Å) oxide MOS capacitors. Both electron and hole tunneling are included in the one-dimensional (1-D) analysis and two new refinements to density-gradient theory are introduced, one relating to the treatment of Shockley-Read-Hall recombination and the other a modification of the tunneling boundary conditions to account for the semiconductor bandgap. Detailed comparisons are made with experimental current-voltage (I-V) data for samples with both n⁺ and p⁺ polysilicon gates and all of the features of the data are found to be understandable within the density-gradient framework. Besides providing new understanding of these experiments, these results show that the density-gradient approach can be of great value for engineering-oriented device analysis in quantum regimes.