Conservation of momentum, and its consequences, in interband resonant tunneling

We have observed a drastic change with temperature (300"4 K) in the line shape of the current-voltage characteristics of GaSb-AlSb-InAs-AlSb-GaSb heterostructures, which below 50 K develop a kink at low biases that is most pronounced at 4 K. This behavior is a direct consequence of the conservation of parallel momentum of electrons and holes participating in interband resonant tunneling, a conservation law that is apparent only at low temperatures because of the small hole Fermi energy. Confirmation of this interpretation is provided by experiments under a magnetic field perpendicular to the tunnel current that show a large peak in the conductance at 6 T. This is the field at which the hole distribution has gained enough parallel momentum to equal the Fermi momentum of electrons.