A simple and reliable process for ohmic contacts to AlxGa1-xAs/GaAs heterostructures is presented. The key feature is the use of niobium refractory metal as a barrier between the eutectic AuGe alloy and the capping Au layer, leading to excellent contact morphology and good electrical properties. Such ohmic contacts fabricated for a two-dimensional electron gas have achieved a resistance of 0.2 Omega mm. The smooth morphology allows subsequent electron beam lithography alignment to the ohmic level, and is crucial for short-gate transistors.