The energy-momentum dispersion relation within the forbidden gap of a single-crystal insulator (in this case, GaSe) has been accurately determined using a simple physical model to describe tunneling currents in appropriate thin-film structures. This dispersion relation, calculated from experimental current-voltage data, is shown to be intrinsic to GaSe and capable of quantitatively predicting tunneling currents. The work reported here represents the first quantitative calculation of tunneling currents in metal-in-sulator-metal structures with all parameters relevant to the experiment independently determined.

• Received 18 May 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.756