Anomalous lateral Zn surface diffusion in InP caused by Zn-contained metallization

We report an anomalous Zn surface diffusion in InP during annealing of ohmic contact structures containing Zn. A Pd/Zn/Pd contact was used to demonstrate this phenomenon. Electrical properties of the contact were monitored to corroborate this anomalous surface diffusion. Cross-sectional scanning electron microscopy was also used to delineate the Zn diffusion front lines. It was found that the Zn surface lateral diffusion can extend ≥50 µm for samples annealed at 500°C or higher temperatures. Close attention should be paid to this anomalous lateral surface diffusion during fabrication of devices using Zn-contained ohmic contacts.