Low resistance, nonalloyed Ohmic contacts to InGaAs

We report extremely low specific contact resistivity (ρc) nonalloyed Ohmic contacts to n-type In0.53Ga0.47As, lattice matched to InP. Contacts were formed by oxidizing the semiconductor surface through exposure to ultraviolet-generated ozone, subsequently immersing the wafer in ammonium hydroxide (NH4OH, 14.8 normality), and finally depositing either Ti∕Pd∕Au contact metal by electron-beam evaporation or TiW contact metal by vacuum sputtering. Ti∕Pd∕Au contacts exhibited ρc of (0.73±0.44)Ωμm2—i.e., (7.3±4.4)×10−9Ωcm2—while TiW contacts exhibited ρc of (0.84±0.48)Ωμm2. The TiW contacts are thermally stable, showing no observable degradation in resistivity after a 500°C annealing of 1min duration.