Using thin films of the layer compound gallium selenide, we have fabricated experimental structures which are nearly ideal for the study of tunneling currents. All of the parameters relevant to current flow in these structures can be independently determined since single-crystal gallium selenide films have the properties of the bulk material and also well-defined interfaces. A new analytical technique for determining the energy-momentum dispersion relation within the forbidden gap of a solid is discussed and applied to current-voltage data obtained from metal-GaSe-metal structures. The resulting $E-k$ relation is shown to be an intrinsic property of GaSe. Tunneling currents in GaSe are shown to be quantitatively understood in terms of this $E-k$ relation, the geometry of a given structure, and a simple model of current flow via tunneling.

• Received 13 January 1971

DOI:https://doi.org/10.1103/PhysRevB.3.3368