A GaN-based Schottky diode incorporating a catalytic Pt thin film and a GaOx dielectric is demonstrated for ammonia (NH3) gas sensing. The GaOx dielectric is formed by a proper hydrogen peroxide (H2O2) treatment on the GaN surface. Based on the effective dissociation of ammonia molecules on Pt surface and suppressed leakage current resulting from the presence of GaOx oxide, the studied Pt/GaOx/GaN Schottky diode exhibits good ammonia sensing performance. Experimentally, a very high sensing response of 252 under 1000 ppm NH3/air gas and an extremely low detection level of 0.4 ppm NH3/air are obtained at 473K, the optimal operating temperature. The sensing speed can be enhanced with an increase in temperature and ammonia concentration. The related response and recovery time constants are compared to those of reported Schottky diode-type ammonia sensors. Therefore, based on these good properties and the advantages of a simple structure and easy fabrication, the studied device provides promise for high-performance ammonia sensing applications.
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