Metals/GaN Catalytic Contact Properties for Hydrogen Gas Sensor Applications

Platinum (Pt), Palladium (Pd) and Nickel (Ni) as catalytic contact are successfully deposited on GaN substrates using dc sputtering method to be utilized as device for sensing hydrogen gas. The catalytic contact formation are studied in terms of its surface morphology and compound formation using atomic force microscopy (AFM) and high resolution X-ray diffraction (HRXRD) respectively, revealing the crystalline properties and uniform deposition of fine grains of the catalytic films. Sample roughness varied from 13.1 (Ni), 18.9.4 (Pd) to 25.4 nm (Pt), increases in parallel to its hydrogen sensing response capability. The formation of hydride compound on Pd and Ni catalytic layer and Ga₃Pt₂ on Pt layer are found to be significant in controlling the sensor response. Device fabricated using Pt as catalytic metal give smallest surface roughness value and capable of forming compound Ga₃Pt₂ with GaN substrate, identified as the main reason in reducing Schottky barrier height of the catalytic metal/GaN. As such, sensor produced using Pt is shown to have the best sensor response performance. Furthermore, surface roughness and compound formation on catalytic metal can be linked directly to sensor performance.