PtTiPtAu and PdTiPtAu ohmic contacts to p-InGaAs

10 nm layers of Pt and Pd were employed as an interlayer between Ti(30 nm)Pt(80 nm)Au(200 nm) metallization and p-InGaAs doped at 1~4×10¹⁹ cm^-3. For the annealing temperatures of 300-500°C, the PtTiPtAu and the PdTiPtAu metallizations exhibited consistently lower contact resistivities than the TiPtAu metallization. The effective barrier height of the PtTiPtAu contacts (0.16 eV) was estimated to be lower than those of the PdTiPtAu contacts (0.14 eV) and the TiPtAu contacts (0.16 eV). The high work function Pt lowered the barrier height. The Pd, on the other hand, formed a favorable interfacial compound when as-deposited, thereby reducing the contact resistivity