A model for multistep trap-assisted tunneling in thin high-k dielectrics

A model for multistep trap-assisted tunneling (TAT) with strong dependence on the trap concentration is introduced. The current density J as a function of the applied voltage V for A1/chemical vapor deposition-Al2O3∕SiO2∕p-Si structures has been measured and fitted for 12 orders of magnitude in a temperature range from T=42K to T=420K. A trap concentration of NT=1.3×1019∕cm3, an electron affinity of eχel=1.7eV, and an effective electron mass of mox=0.28m0 (m0 is the electron rest mass) for the Al2O3 are used. A single set of parameters fits the leakage currents of all samples with different Al2O3 thicknesses at all temperatures.