TUNNELING PROCESSES BETWEEN QUANTUM WIRES AND 2-DIMENSIONAL ELECTRON-STATES

We have studied tunneling processes between two independently contacted two-dimensional electron gas systems, which are separated by a barrier of 195 angstrom. Resonant tunneling processes between the quantized states in the different channels. Structuring the upper channel into quantum wires, we also investigate tunneling processes between states of different dimensionality. By analyzing the transition rules, we explain the features of the tunneling characteristics and determine quantitatively the subband energies. Subband spacings up to 4.5 meV are obtained from the experimental data and are verified by the results of a two-dimensional self-consistent model. These extremely high values are a consequence of a Ge diffusion during the contact formation process, which suggests that an appropriate surface treatment after quantum wire fabrication can be used to increase the quantization energies.