Comprehensive study of Pd/GaN metal–semiconductor–metal hydrogen sensors with symmetrically bi-directional sensing performance

Ammonia sensing characteristics of a Pt/AlGaN/GaN Schottky diode

“…This also provides the benefit of sensing performance. Previous reports of Schottky diode-type gas sensors were mainly focused on hydrogen sensing performance [13][14][15][16][17]. In this work, an interesting Pt/AlGaN/GaN Schottky diode is illustrated to study the ammonia sensing current-voltage (I-V) characteristics for the first time.…”

Sensing mechanisms of Pt/β-Ga2O3/GaN hydrogen sensor diodes

“…However, since hydrogen gas tends to be flammable and explosive when its concentration in air exceeds more than 4% at room temperature, a reliable detection of its presence certainly becomes one of important safety issues to consider. Because there are impending needs for robust gas sensors operating in harsh environments, semiconductor-based hydrogen gas sensors have thus attracted much attention [1]; some of these devices being reported previously are based on Si [2], SiC [3] and GaN semiconductors [4], just to name a few. Due to the inherent natures of high electron saturation velocity, high breakdown electric field, and superior thermal and chemical stabilities, GaN-based hydrogen sensors have started to emerge as the main device focus of considerable interest.…”

Hydrogen sensors with double dipole layers using a Pd-mixture-Pd triple-layer sensing structure

“…Previous reports indicated similar trends to our work and inferred that a shorter response time in a higher [H 2 ] ambience is due to more hydrogen molecules being dissociated into hydrogen atoms. Our previous work in [18,19] reported that Pd-deposited GaN hydrogen sensors showed a response time shorter than that of Pd-mixture-deposited GaN hydrogen sensors. By comparison, the present Pd-mixture-Pd-deposited GaN hydrogen sensor has a much longer response time at similar concentration of H 2 .…”

“…Commonly accepted sensing sequences for these kinds of hydrogen sensors are as: the hydrogen molecules are adsorbed and dissociated at a Pd (or Pt) surface, followed by rapid diffusion of H atoms to the Pd-semiconductor (or Pd-insulator) interface where the dipole layer is formed to result in the lowering of Schottky barrier height and the increase of a sensing current. Recently, Chiu et al reported a new metal-semiconductor-metal (MSM) hydrogen sensor [19] and employed a mixture of Pd and SiO 2 as the sensing metal [20]. Unlike commonly studied MS and MIS hydrogen sensors, symmetrically bi-directional sensing characteristics were addressed in their MSM hydrogen sensor.…”