A Novel $\hbox{Pt/In}_{0.52}\hbox{Al}_{0.48}\hbox{As}$ Schottky Diode-Type Hydrogen Sensor
On the basis of a Pt/In0.52Al0.48As metal-semiconductor structure, a novel hydrogen sensor is fabricated and demonstrated. The studied Pt/In0.52Al0.48As Schottky diode-type hydrogen sensor exhibits significant sensing performance including high relative sensitivity ratio of about 2600% (under the 1% H2/air gas and VR=-0.5 V at 30 degC), large current variation of 310 muA (under the 1% H2/air gas and VR=-5 V at 200 degC), 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 Omega, respectively (under the 1% H2/air gas at 30 degC). The hydrogen concentrations and operating temperatures tested in this letter are in the range of 15 ppm-1% H2/air and 30 degC-250 degC, respectively. Based on the excellent integration compatibility with InP-based electronic devices, the studied device provides the potentiality in high-performance sensor-array applications
Hydrogen sensing characteristics of Pd- and Pt-Al0.3Ga0.7As metal–semiconductor (MS) Schottky diodes
Pd- and Pt-Al0.3Ga0.7As metal–semiconductor (MS) Schottky diodes are fabricated and studied. The hydrogen-sensing characteristics including Schottky barrier height modulations and hydrogen detection sensitivity and transient responses are investigated and presented. Due to the formation of hydroxyl at higher temperature, different transient responses are found for the studied Pt- and Pd-MS Schottky diodes. According to the van't Hoff equation, the initial heat of adsorption for the Pd- and Pt-Al0.3Ga0.7As MS interfaces is calculated as −5.21 and −7.56 kJ mole−1, respectively.
Quantitative spectroscopy of substitutional nitrogen in GaAs1−xNx epitaxial layers by local vibrational mode absorption
Fourier transform infrared absorption measurements have been performed on thin films of GaAs1−xNx grown by metalorganic chemical vapour deposition or molecular beam epitaxy on semi-insulating GaAs substrates. The local vibrational mode absorption due to NAs is used to assess the substitutional nitrogen fraction. Based on a comparison with secondary ion mass spectroscopy and x-ray diffraction analysis, the calibration factor for the integrated absorption is derived. Quantitative determination of substitutional nitrogen is possible up to x ≈ 0.05, in epitaxial layers of thicknesses down to 10–100 nm.