Electroless deposition of palladium films on gallium nitride for Schottky diodes

This work presents electroless deposition of palladium films onto gallium nitride from aqueous palladium dichloride using sodium L-ascorbate as the reducing agent in an acidic bath. Profilometry, four-point probe measurements, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to measure film thickness, sheet resistance, resistivity, morphology, and composition. The resistivity of Pd was 1–3 × 10–5 Ω cm. Schottky diodes were produced from plated films, and the barrier heights and ideality factors were determined from current–voltage measurements. Average barrier heights were 1.13–1.26 eV, with ideality factors from 1.02 to 1.05, depending on the gallium nitride epilayer and substrate. A method for depositing palladium-gallium alloy films is also presented onto gold surfaces from palladium dichloride and gallium (III) sulfate using sodium hypophosphite as the reducing agent; however, palladium-gallium alloys were not readily deposited on gallium nitride.