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 the Schottky barrier height of Ru contacts from 0.49 eV before passivation to about 0.88 eV after passivation and annealing at 125 degrees C. Furthermore, a corresponding decrease in reverse leakage current of more than three orders was also obtained by passivation. The corresponding 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/InP ohmic contacts showed remarkable improved surface morphology after rapid thermal annealing, in comparison with the standard Au/Ni/Au-Ge/InP rapid thermal annealed (RTA) ohmic contacts. The Ru-containing contacts also showed a lower minimum specific contact resistance value of 1 x 10(-7) Omega cm(2), after 400 degrees C RTA. From comparative electrical, SEM and Auger electron spectroscopy (AES) investigations, if is clear that Ru has various advantages as a very effective diffusion barrier for ohmic contacts on InP.