Ohmic contacts to heavily carbon-doped p-AlxGa1−xAs

Two different metallization schemes, AuBe(80 nm) and Pt(75 nm)/Ti(50 nm), were investigated as potential ohmic contacts for highly carbon-doped p-AlxGa1−xAs. The best contact resistance values of 0.015 and 0.025 Ω mm were achieved by applying the Pt/Ti scheme onto 1×1020 and 1×1019 cm−3 C-doped AlGaAs, respectively, followed by rapid thermal processing at 450 °C. The AuBe contacts yielded their lowest values of 0.025 and 0.05 Ω mm for the same doping levels as a result of rapid thermal processing at 425 °C. The heat treatment at 450 °C caused only limited reactions in both the Pt/Ti and Ti/AlGaAs interfaces and did not lead to significant degradation of the stable microstructure.