Antimony Passivation of InP

Antimony passivation of InP was investigated. Sb was evaporated on a HCl-etched InP substrate and annealed at 300°C for 10 min. I-V characteristics of the Au/Sb/InP diode are substantially improved and the Schottky barrier height becomes higher as compared with the conventional Au/InP diode. The reverse current decreases by about two orders of magnitude upon Sb passivation. X-ray photoelectron spectroscopic (XPS) measurements show that the Sb oxide, Sb2O3, is formed near both the surface and the interface, i.e., the Sb2O3/Sb/Sb2O3 layered structure exists on the InP substrate. On the other hand, In2O3, the dominant component species of the native oxide of InP, is not observed in the Sb-passivated sample, which indicates that Sb passivation effectively removes that native oxide (In2O3) and suppresses reoxidation of the InP surface. Sb is considered to reduce In2O3 and is oxidized itself to become Sb2O3. This is a probable mechanism of Sb passivation. After the Sb-passivated substrate is washed in deionized water, the amount of Sb decreases and In2O3 is again observed. This is explained by the balance in the chemical reaction between In2O3 and Sb2O3 (the mass-action law). The low Schottky barrier height and the poor electrical characteristics are thus well correlated with the existence of the native oxide of InP, dominantly, In2O3.