Interfacial microstructures of Pd/Ge/Ti/Au ohmic contact to n-type GaAs have been investigated using cross-sectional transmission electron microscopy, and the results are used to interpret the electrical properties. Annealing at 300°C yields a contact resistance of 0.62 Ω mm and the layer structure is changed to GaAs/PdGe/Au4Ti/TiO. The ohmic contact is formed through a solid phase regrowth of GaAs heavily doped with Ge below the PdGe layer. At 380°C, the lowest contact resistance of 0.43 Ω mm is obtained. The layer structure is changed to GaAs/(Ge-Ti)/PdGe/TiO. Spikes composed of Au and AuGa are found at the grain boundaries of the PdGe compound. The formation of AuGa at 380°C reduces the contact resistance through the creation of more Ga vacancies at the interface of GaAs/PdGe, and the incorporation of elemental Ge.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)