ABSTRACT
Electronic transport in modulation-doped GaAs-AlGaAs heterostructures can no longer be regarded as diffusive. Instead, low-energy electron propagation is ballistic and a large fraction of the carriers traverse typical device distances without a serious scattering event. On one hand, such extraordinary electronic transport can seriously alter the low-temperature performance of traditional devices that are based on high mobility 2D electron systems. Beams of 2D ballistic electrons can be created and they are able to intersect each other with negligible interaction. High-mobility, two-dimensional electron systems, combined with modern lithographic techniques, lend themselves at low temperatures to the implementation of a wide variety of control elements that closely resemble the devices portrayed in textbooks on geometrical optics. Regions totally depleted of 2D electrons such as mesa edges and under highly biased gates act as almost perfect electron reflectors. Partially depleted regions refract electrons in accordance with an equivalent of Snell’s law in optics.
