Refractory Metal Contacts to N-Type InP and InGaAs

W/ Ti refractory metal ohmic contacts to η-type InP and InGaAs have been fabricated by electron-beam evaporation in an ultra-high vacuum metallization system. Excellent surface morphology was observed and good pattern transfer of the metal films was achieved with chemical etching. Ideal ohmic behavior was obtained for samples which were heavily doped either during MBE growth or via ion implantation. The lowest specific contact resistances obtained were: 4.8×10−7Ωcm2 for ion implanted n+InP and 4.9×10−6 Ωcm2 for n+InGaAs. The thermal and metallurgical stability of the contacts has been investigated using scanning electron microscopy and Auger electron spectroscopy with sputter depth profiling. The contact samples were subjected to heat treatments using rapid thermal annealing at temperatures of 350 to 800°C. Scanning electron microscopy showed that after annealing at up to 600°C no degradation in surface morphology had occurred. Auger depth profiling indicated that the W-film maintained a sharp interface for all heating treatments, with no degradation up to 600°C. However, some Ρ and In was found at the surface of the contact layer after annealing at 800°C.