Resonant tunneling of three-dimensional electrons into degenerate zero-dimensional levels

A series of current peaks is observed at the onset of tunneling current in three-dimensionally confined tunneling diodes. The respective neighboring current peaks have an equivalent amplitude difference, which is independent of the diode lateral size. We interpret these peaks as being due to the tunneling of a three-dimensional emitter electron at the Fermi energy through the zero-dimensional well levels. The peak current is defined by the degeneracy of the zero-dimensional level confined by a harmonic lateral potential.