Low-dimensional quantum devices

Novel submicron devices can now be made from extremely pure crystals containing small numbers of electrons. Using these structures the fundamentals of quantum mechanics can be studied in which fitting theory to experiment only requires the material parameter of effective mass to be known. In this article I will discuss how the technological advances in the semiconductor industry, developed to produce the next generation of micro-chips, have been appropriated by the physics community to test how electron transport processes vary when devices are made smaller than some important physical length scales. Most of the devices I will discuss are made using a two-dimensional electron gas trapped at the interface between GaAs and AlGaAs. This is then laterally patterned to force current transport through a small region. Devices have been demonstrated in which electrons traverse the device without scattering (one-dimensional ballistic conductance), while other devices reveal the nature of single electron transport (zero-dimensional dots). The quantum mechanical wave nature of electron transport is very elegantly shown in devices which mimic optical apparatus such as Fabry - Pérot interferometers and lenses. The application of a strong magnetic field to zero-dimensional devices reveal phenomena remarkably similar to the Aharonov - Böhm effect seen in metal loops. This tells us a great deal about how a magnetic field applied to a two-dimensional electron gas forces electrons to travel around the edge of a device. This review was received September 1995