Si implant-assisted ohmic contacts to GaN

We show that the specific contact resistance, pc, of Ti/Al/Ni/Au contacts can be reduced by up to two orders of magnitude to a record low of 2.7 x 10^-8 ¿-cm² by implanting and annealing the GaN at 1200°C for 10 min with annealing and the initial doping concentration playing important roles along with the implant. Our AFM results suggest that the preferential evaporation of N is not an important factor because the surface was protected by our patented annealing cap, composed of a thin low temperature MOCVD (metal-organic chemical vapor deposition) AlN adhesion layer and a thicker sputtered A1N mechanical layer.