Highly functional tunnelling devices integrated in 3D

Abstract We present a new technology for integrating tunnelling devices in three dimensions. These devices are fabricated by the combination of the growth of semiconductor heterostructures with the controlled introduction of metallic elements into an epitaxial layer by an overgrowth technique. First, we use a new type of tunnelling transistor, namely a resonant‐tunnelling permeable base transistor. A simple model based on a piece‐wise linear approximation is used in Cadence to describe the current–voltage characteristics of the transistor. This model is further introduced into a small signal equivalent circuit in order to optimize the performance of the device. In addition to the tunnelling structure below the grating, these transistors may be integrated in 3D by the introduction of another tunnelling structure directly over the metal grating. In the integrated device structure, the gate acts simultaneously on both tunnelling structures and the obtained characteristics are the result of the interplay between the two tunnelling structures and the gate. An equivalent circuit model is developed and we show how this interaction influences the current–voltage characteristics. The gate may be used to adjust the peak voltage of certain peaks in a controlled fashion, which creates a highly functional tunnelling device. These results show the need for a strong interaction between the development of circuit models and processing technology to develop new nano‐electronic devices and circuits. Copyright © 2003 John Wiley & Sons, Ltd.