Effect of Pt Interlayer on Low Resistivity Ohmic Contact to p-InP Layer and Its Optimization

The contact characteristic between p-InP and metal plays an important role in InP-related optoelectronic and microelectronic device applications. We investigate the low-resistance Au/Pt/Ni and Au/Ni ohmic contacts to p-InP based on the solid phase regrowth principle. The lowest specific contact resistivity of Au(100 nm)/Pt(115 nm)/Ni (50 nm) can reach 2.64 \times 10^-6\,\Omega \cdotcm^2 after annealing at 380 ℃ for 1 min, while the contact characteristics of Au/Ni deteriorated after annealing from 340 ℃ to 480 ℃ for 1 min. The results of scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy show that the Pt layer is an important factor in improving the contact characteristics. The Pt layer prevents the diffusion of In and Au, inhibits the formation of Au_3In metal compounds, and prevents the deterioration of the ohmic contact. The metal structures and optimized annealing process is expected to be helpful for obtaining high-performance InP-related devices.