Hydrogen Sensing Characteristics of a Pd/AlGaN/GaN Schottky Diode

Abstract

In this paper, the interesting hydrogen sensing properties of a Pd-gate AlGaN/GaN Schottky diode are investigated. A significantly low detection limit of 850 ppb H2/air gas can be observed with increasing the temperature to 423 K. The experimental results indicate that hydrogen molecules cause great influences on the diode breakdown voltage. Also, the diode exhibits an ultrahigh sensing response of 2.04×105 at 423 K when exposure to a 9660 ppm H2/air gas. The transient response time and reversibility of the studied device can be improved by increasing the operating temperature.

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

“…Subsequently, hydrogen atoms dissociated by Pt metal permeate through the metal bulk to reach the metal-semiconductor (M-S) interface. It is known that hydrogen atoms at the M-S interface could be polarized to form a dipolar layer by the internal electric field [12,17,20]. This leads to the hydrogeninduced Schottky barrier height variation.…”

“…GaN-based Schottky-type gas sensors show less pinning-effect of Fermi level. This leads to the high gas detecting sensitivity [12]. In addition, AlGaN/GaN interface could exhibit a high-density twodimensional electron gas (2-DEG) due to the piezoelectric and spontaneous polarizations [13].…”

On a Schottky diode-type hydrogen sensor with pyramid-like Pd nanostructures

“…This can be attributed to that more hydrogen molecules are effectively dissociated into hydrogen atoms, and result in the increased lowering effect of Schottky barrier height under higher hydrogen concentration [18]. In addition, at higher temperature, the sticking coefficient would be decreased which leads to less adsorbed hydrogen atoms at Pd/AlGaN interface [22]. For instance, a maximum (minimum) value of 19.7% (1.1%) upon exposing to a 1% (10 ppb) H 2 /air gas at 300 K is found.…”

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

“…When a 10,000 H 2 /air gas is introduced, the estimated S values are 9.3, 13.7, 11.6, and 10.3%, respectively, at 300, 400, 500, and 600 K. Under the same hydrogen-contained ambiences, the maximum response S is found at a temperature of 400 K. This is due to the increase of effective dissociation of hydrogen molecules which certainly enhances the sensing response S in a lower temperature range (T < 400 K) [41]. Yet, the decrease in sensing response S at higher temperature (T > 400 K) mainly results from the decrease in the hydrogen sticking coefficient which leads to fewer hydrogen atoms being adsorbed at the Pt/AlGaN interface.…”

“…Yet, the decrease in sensing response S at higher temperature (T > 400 K) mainly results from the decrease in the hydrogen sticking coefficient which leads to fewer hydrogen atoms being adsorbed at the Pt/AlGaN interface. On the other hand, at a fixed temperature of 400 K [41], the S values of the EP Pt-gate HFET are 1.5, 3.7, 5.5, 7.4, 9.0, and 13.7%, respectively, under hydrogen concentrations of 5, 50, 200, 500, 1000, and 10,000 ppm H 2 /air. In general, the S is increased in proportion to the increase in hydrogen concentration.…”