Transport through an array of small ohmic contacts alloyed to the two-dimensional electron gas of a GaAs/AlGaAs heterostructure

We investigate transport through a two-dimensional electron gas (2DEG) underneath a submicron periodic array of small Ge-AS alloyed ohmic contacts and compare the results with the resistance of the small contacts, We find that as the contacts form, the effective mobility of the 2DEG underneath the array decreases and that the carrier concentration between the small contacts is reduced. From the low-field magnetoresistance we are able to identify ballistic cyclotron orbits; commensurate with the period of the array. Wt find that reducing the diameter of the ohmic metallization to 0.2 mu m severely inhibits ohmic contact formation. (C) 1996 American Institute of Physics.