The current–voltage (I-V) characteristics for a metal-insulator-heavily-doped semiconductor structure are computed numerically by solving the time-dependent Schro¨dinger equation. The Fowler–Nordheim tunneling expression was found to be inappropriate to estimate the barrier potential nor found to fit the experimental results at both high and low applied fields. It is shown also that the computedI–Vcharacteristic curves agree well with the recently published experimental data forTa-Sn-OandTa2O5films at the high as well as low fields.©1998 American Institute of Physics.