THE ROLE OF RU IN IMPROVING SCHOTTKY AND OHMIC CONTACTS TO INP

Wet chemical passivation of InP was performed in an acid solution that contained Ru ions in solution. Results showed a drastic increase in t he Schottky barrier height of Ru contacts from 0.49 eV before passivat ion to about 0.88 eV after passivation and annealing at 125 degrees C. Furthermore, a corresponding decrease in reverse leakage current of m ore than three orders was also obtained by passivation. The correspond ing value for the ideality factor was 1.16. The higher barrier height was related to the XPS results, which showed a decrease in the amount of oxidized indium and phosphorus after passivation. Au/Ru/Au-Ge/Ni/In P ohmic contacts showed remarkable improved surface morphology after r apid thermal annealing, in comparison with the standard Au/Ni/Au-Ge/In P rapid thermal annealed (RTA) ohmic contacts. The Ru-containing conta cts also showed a lower minimum specific contact resistance value of 1 x 10(-7) Omega cm(2), after 400 degrees C RTA. From comparative elect rical, SEM and Auger electron spectroscopy (AES) investigations, if is clear that Ru has various advantages as a very effective diffusion ba rrier for ohmic contacts on InP.