Submicron Ni/Au/Ge contacts to an AlGaAs/GaAs two-dimensional electron gas*

We report on the results of a study to optimize submicron alloyed ohmic contacts to the two-dimensional electron gas (2DEG) in AlGaAs/GaAs heterostructures. We vary the geometry, annealing parameters, and metal orientation relative to the crystallographic axes of the host GaAs crystal to determine the optimal parameters for low resistance contacts and to study the mechanisms that limit the formation of Ohmic behavior for very small areas. We discuss both electrical and structural characterization data. Our study has generated contact resistance below 600 Ω for contact areas <1 um².

 

Work supported by the Quantum Science Center at Oak Ridge National laboratory under contract number DE-AC05-00OR22725.