The 2DEG formed at a selectively doped heterojunction has enabled a large
amount of basic physics research. The electron transport in confined
geometries is of high principal interest. Using a strong magnetic field applied
perpendicular to a 2DEG, K. von Klitzing discovered the quantum Hall effect
(Nobel Prize 1985) in samples supplied by M. Pepper and G. Dorda. Using
even higher fields, D.C. Tsui and H.L. Stoermer (Nobel Prize 1998) discovered
the fractional quantum Hall effect in ultrapure MBE material made by A.C.
Gossard.