Many interesting and new phenomena are predicted to occur for a three dimensional electron gas where scattering by the background of point charges is absent. Strong magnetic fields in the quantum limit are predicted to induce collective charge- or spin- density wave states with novel transport properties analogous to the quantum Hall effect. With their collaborator, A.C. Gossard, they have developed means of producing spatially uniform layers of elctron gas using wide remotely doped parabolic gallium arsenic/aluminumxgallium1-xarsenic wells, which can be thick enough to approach the three-dimensional limit. The parabolic potential, created using parabolic grading of the average aluminum concentration, appears to the electrons as a spatially uniform positive background charge. They propose to investigate magnetotransport in strong magnetic fields at dilution refrigerator temperatures in order to study the changes which occur in the quantum Hall effect as the electron layer becomes thicker, and to search for new collective phenomena. These heterostructures will be characterized using optical and far- infrared measurements of the quantum excitation spectra of electrons, as well as measurements of Shubnikov de Haas oscillations in the magnetoresistance.
