On the hydrogen sensing characteristics of a Pd/AlGaN/GaN heterostructure field-effect transistor (HFET)

Hydrogen sensing characteristics of a Pt/AlGaN/GaN heterostructure field-effect transistor (HFET) prepared by sensitization, activation, and electroless plating (EP) approaches

“…Table 3 lists a comparison between the studied EP Pt-gate HFET and other HFETs. As compared to other works [34][35][36][37][38][39]42,45], the studied EP Pt-gate HFET presents robust thermal stabilities and excellent hydrogen sensing performance. Notably, the significantly high rectification ratio R of the studied EP Pt-gate HFET demonstrates superior switching performance under hydrogen-contained ambiences.…”

“…Due to the built-in electric field, resulting from a depletion region at the AlGaN Schottky contact layer, hydrogen atoms adsorbed at the Pt/AlGaN interface are polarized and form a dipole layer. This dipole layer induces an additional voltage at the Pt/AlGaN interface and changes the effective gate Schottky barrier height [18,39]. This modulation of Schottky barrier height brings about the change in 2-D electron gas (2DEG) density in the GaN channel.…”

“…This signifies that the current variation could still be measured for the EP Pt-gate HFET after exposure to an extremely low concentration of hydrogen gas. When the hydrogen gas is introduced, hydrogen sensing behaviors of the EP Pt-gate HFET could be defined by a drain current response S(%) as [39]:…”

Pt-AlGaN/GaN HEMT-Sensor for Hydrogen Sulfide (H2S) Detection

“…The detection mechanism involves the dissociation of H2S molecules into S and H atoms at the surface of Pt electrode. H atoms subsequently diffuse to the metal-semiconductor interface, where dipoles form and lower the built-in electric field, causing a reduction of the Schottky barrier height and an increase in IDS [6]. The signal repeatability for 20 ppm H2S is shown in Figure 3b, with gas injection/purge duration of 15/60 min.…”

Pt-AlGaN/GaN HEMT-sensor layout optimization for enhancement of hydrogen detection

“…AlGaN/GaN sensors with various gate electrode dimensions have been previously reported. Large gate area devices have been reported [3,6,7] with Wg/Lg ratios of 7, 1 or 5 respectively, while others [8,9] used typical HEMT layouts with a few micron length and large width resulting in ratios on the order of 100. However the reasons for the design choices were not stated.…”