On the basis of a Pt/In 0.52 Al 0.48 As metalsemiconductor structure, a novel hydrogen sensor is fabricated and demonstrated. The studied Pt/In 0.52 Al 0.48 As Schottky diode-type hydrogen sensor exhibits significant sensing performance including high relative sensitivity ratio of about 2600% (under the 1% H 2 /air gas and V R = −0.5 V at 30 • C), large current variation of 310 µA (under the 1% H 2 /air gas and V R = −5 V at 200 • C), widespread reverse-voltage regime (0 ∼ −5 V), stable hydrogen-sensing current-voltage (I-V ) curves, and fast transient response time of 1.5 s. The calculated Schottky barrier-height change and series-resistance variation, from the thermionic-emission model and Norde method, are 87.0 meV and 288 Ω, respectively (under the 1% H 2 /air gas at 30 • C). The hydrogen concentrations and operating temperatures tested in this letter are in the range of 15 ppm-1% H 2 /air and 30 • C-250 • C, respectively. Based on the excellent integration compatibility with InP-based electronic devices, the studied device provides the potentiality in high-performance sensor-array applications.Index Terms-In 0.52 Al 0.48 As, Pt, relative sensitivity ratio, reverse voltage, Schottky diode.
A new hydrogen sensor based on a GaAs-based high electron mobility transistor (HEMT) with a catalytic Pt-oxide-Al0.24Ga0.76As (MOS) gate structure is fabricated and demonstrated. The threshold voltage shift, hydrogen detection sensitivity, and transient responses of the device under different hydrogen concentrations and temperature are measured and studied. Based on the transistor amplification action, even at an extremely low hydrogen concentration of 14ppm H2/air, the studied device shows significant drain current variation (about 0.12mA). Furthermore, the studied device can be operated under wider operating temperature regimes with remarkable hydrogen-sensing properties. The decreased hydrogen detection capability with increasing operating temperature demonstrates the exothermic reaction of the hydrogen adsorption and desorption processes.
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