MODELING OF THE STATIC PROPERTIES FOR DOUBLE-DELTA TRANSISTORS

Molecular-beam epitaxy of silicon permits the growth of any layers des ired on large areas with a high reproducibility. A vertical arrangemen t of several thin ''delta layers'' in combination with local epitaxy a nd selective etching leads to a new kind of electron device using the third dimension. With a delta layer thickness of about 2 nm and by var ying other device dimensions within a few nanometers, electron devices with threshold voltages on the order of magnitude of a few volts were possible. Selective contacts to the individual delta layers permit ve rtical transport studies. In the resistance-gate voltage characteristi c of a vertical double-delta transistor with an effective gate length of about 90 nm periodic oscillations are clearly observed. It can be s hown that in the transistor, three two-dimensional electron systems me et each other perpendicularly. The calculation of the electronic struc ture of the device is carried out with a simple but reasonably exact m ethod. The calculated eigenvalue spectrum corresponds well with the ob served oscillations in the experimental resistance-gate voltage charac teristic and permits its interpretation.