Submicron conducting channels defined by shallow mesa etch in GaAs-AlGaAs heterojunctions

A new approach to the lateral confinement of electrons in the two-dimensional electron gas of GaAs-AlGaAs heterojunctions has been developed. The electrons are electrostatically confined by a shallow mesa structure etched in the upper n-doped AlGaAs layer. This structure is fabricated using electron beam lithography and reactive ion etching. The undoped AlGaAs spacer layer is not removed in order to avoid mobility degradation and channel depletion. Long narrow channels have been made for the study of electrical transport properties. The effective channel width in the submicron range is smaller than the width of the mesa structure. Preliminary low-temperature magnetoresistance data are presented.