Alloyed ohmic contacts to two-dimensional electron system in AlGaAs/GaAs heterostructures down to submicron length scale

We have realized and investigated Au/Ge/Ni alloyed ohmic contacts to two-dimensional electron systems (2DES) embedded in various Al0.67Ga0.33As/GaAs heterostructures. Transport and geometrical investigations have been carried out to understand fundamental properties of these contacts. A recipe for creating low resistive and reliable alloyed ohmic contacts to 2DES is given, which is successful even for contacts to deep lying 2DES and contact sizes down to submicron length scale (View the MathML source). The contact resistance between 2DES and alloyed metal depends on the length and orientation of the interface line between 2DES and alloyed metal relative to the crystal orientation of the heterostructure.