MOMENTUM CONSERVATION IN 1D-2D TUNNELING PROCESSES

Using tunneling spectroscopy, we have investigated two independently contacted two dimensional electron gas systems, which are separated by a barrier of 195 angstrom. As the electron momentum parallel to the barrier is conserved for 2D-2D tunneling, resonances in the tunneling characteristics dI/dV are observed each time, a subband in one 2D channel matches a subband on the other side of the barrier. Structuring the upper 2D-channel into quantum wires, we also investigate tunneling processes between states of different dimensionality. Momentum conservation in the direction of free motion in the quantum wires leads to resonances in the tunneling characteristics each time 1D and 2D subband are aligned energetically. As the electron momentum in the direction of 1D confinement is not conserved any longer, we also observes situations, where the 2D-Fermi level matches the 1D subband energies. These two types of transitions are, directly distinguished by a different temperature behavior of the corresponding peak amplitudes.