Improved hydrogen sensing characteristics of a Pt/SiO 2/GaN Schottky diode

Abstract

The hydrogen sensing and response characteristics of Pt/GaN (metal–semiconductor, MS) and Pt/SiO 2/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 ( S F) of 609 (MS) and 14,690 (MIS) (in 9970 ppm H 2/air), reverse-bias hydrogen response ( S R) of 5630 (MS) and 44,640 (MIS) (in 9970 ppm H 2/air), Schottky barrier height variation (Δ ϕ b) of 195.9 (MS) and 231.6 meV (MIS) (in 9970 ppm H 2/air), respectively. Based on the equilibrium adsorption analysis, the hydrogen adsorption enthalpy (Δ H°) 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 ( τ a) 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 ( E a) 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/SiO 2/GaN (MIS) Schottky diode exhibits a promise for high performance hydrogen sensor applications.