Improved hydrogen sensing characteristics of a Pt/SiO2/GaN Schottky diode

The hydrogen sensing and response characteristics of Pt/GaN (metal–semiconductor, MS) and Pt/SiO2/GaN (metal–insulator–semiconductor, MIS) Schottky diodes under different-concentration hydrogen gases are studied over a wide temperature range in an air atmosphere. Experimentally, the studied MS and MIS devices exhibit hydrogen sensing performance, including forward-bias hydrogen response (SF) of 609 (MS) and 14,690 (MIS) (in 9970 ppm H2/air), reverse-bias hydrogen response (SR) of 5630 (MS) and 44,640 (MIS) (in 9970 ppm H2/air), Schottky barrier height variation (Δϕb) of 195.9 (MS) and 231.6 meV (MIS) (in 9970 ppm H2/air), respectively. Based on the equilibrium adsorption analysis, the hydrogen adsorption enthalpy (ΔH°) of the studied MS and MIS devices are −10.21 kJ/mol and −19.5 kJ/mol, respectively. The studied MIS device further shows the excellent performance for high temperature detection and improved activity of hydrogen adsorption reaction. Experimentally, the hydrogen detection adsorption time constants (τa) of the studied MS and MIS devices decrease from 25 to 3 s and from 12 to 2 s, respectively, as the temperature increases from 300 to 700 K. In addition, according to the kinetic adsorption analysis, the activation energy (Ea) of the studied MS and MIS devices are 4.498 kJ/mol and 2.885 kJ/mol, respectively. This implies that the studied MIS device can also perform more rapid hydrogen detection. Therefore, the studied Pt/SiO2/GaN (MIS) Schottky diode exhibits a promise for high performance hydrogen sensor applications.