Molybdenum germanide ohmic contact to n-GaAs

GeMo refractory ohmic contacts for n-type GaAs with a specific contact resistivity as low as 10-6¿cm2 have been obtained on 1018cm-3 epitaxial layers. This low resistivity was obtained by contact annealing under As overpressure. Contacts using As-doped Ge layers and annealed without As overpressure have also been realised; in this case the obtained resistivity was 5 × 10-6¿cm2. The ohmic contact formation resulted from the creation of an n + layer by Ge overdoping and the formation of a molybedenum germanide stable phase.