Hydrogen sensing properties of a GaN/AlGaN-based Schottky diode with a catalytic platinum (Pt) hybrid structure

A new hydrogen sensor, based on a Schottky diode incorporated with a GaN/AlGaN heterostructure and catalytic platinum (Pt) hybrid metals, is fabricated and studied. The Pt hybrid metals include an evaporated Pt thin film and Pt nanoparticles (NPs). Pt NPs are formed by a solution-based process and an adequate post annealing treatment. The presence of Pt NPs gives the "spill-over" effect and increases the surface area/volume (SA/V) ratio and catalytic activity of the Pt metal. Hence, the related hydrogen sensing performance can be improved. Experimentally, a very high sensing response of 2.7 x 106 (@1% H-2/air) with short response and recovery times of 17 s and 23 s and an extremely low detecting level of 1 ppm H-2/air are obtained at 300 K. Widespread detecting ranges on the hydrogen concentration and operating temperature are acquired. Based on the theoretical analyses, an exothermic reaction of the hydrogen adsorption process with an activation energy Ea of 15.47 kJ/mol and an enthalpy change Delta H degrees of-11.4 kJ/mol for the studied Pt NP/Pt film/GaN/AlGaN device is observed. The studied device is therefore promising for high-performance hydrogen sensing applications.