Very low resistance alloyed Ni-based ohmic contacts to InP-capped and uncapped n⁺-In_0.53 Ga_0.47As

Successful application of the silicide-like Ni_xInGaAs phase for self-aligned source/drain contacts requires the formation of low-resistance ohmic contacts between the phase and underlying InGaAs. We report Ni-based contacts to InP-capped and uncapped n⁺- In_0.53Ga_0.47As (N_D = 3 × 10¹⁹cm^-3) with a specific contact resistance (ρc) of 4.0 × 10^-8± 7 × 10^-9 Ω·cm² and 4.6 × 10^-8± 9 × 10^-9 Ω·cm², respectively, after annealing at 350 °C for 60 s. With an ammonium sulfide pre-metallization surface treatment, ρc is further reduced to 2.1 × 10^-8± 2 × 10^-9 Ω·cm² and 1.8 × 10^-8± 1 × 10^-9 Ω·cm² on epilayers with and without 10 nm InP caps, respectively. Transmission electron microscopy reveals that the ammonium sulfide surface treatment results in more complete elimination of the semiconductor's native oxide at the contact interface, which is responsible for a reduced contact resistance both before and after annealing.