Ion implantation for unalloyed ohmic contacts to AlGaN/GaN HEMTs

We report on the use of Si ion implantation for the fabrication of AlGaN/GaN HEMTs with an as-deposited ohmic contact resistance of 0.4 Ωmm. Currently ohmic contact technology requires a high temperature (∼870°C) alloying step. The resulting contacts have an irregular shape and surface that can create difficulties in device reproducibility, reliability and yield, particularly for large periphery devices. The use of ion implantation to enable unalloyed ohmic contacts has the potential to reduce these obstacles to the manufacturability of AlGaN/GaN HEMTs. Using ion implantation also has the potential to reduce access resistance by reducing ohmic contact resistance and gate-source spacing, to eliminate the need for etched device isolation, and to enable sophisticated device designs that take advantage of lateral dopant engineering.