Department of Electrical and Electronics Engineering
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Item Thermodynamic analysis of acetone sensing in Pd/AlGaN/GaN heterostructure Schottky diodes at low temperatures(Elsevier, 2016-03) Kumar, RahulAn AlGaN/GaN heterostructure based metal–semiconductor–metal symmetrically bi-directional Schottky diode sensor structure has been employed to investigate acetone sensing and to analyze thermodynamics of acetone adsorption at low temperatures. The AlGaN/GaN heterostructure has been grown by plasma-assisted molecular beam epitaxy on Si (111). Schottky diode parameters at different temperatures and acetone concentrations have been extracted from I–V characteristics. Sensitivity and change in Schottky barrier height have been studied. Optimum operating temperature has been established. Coverage of acetone adsorption sites at the AlGaN surface and the effective equilibrium rate constant of acetone adsorption have been explored to determine the endothermic nature of acetone adsorption enthalpy.Item Fast Response (7.6s) Acetone Sensing by InGaN/GaN on Si (111) at 373 K(IEEE, 2017-03) Kumar, RahulA new and exciting resistive gas sensor based on Ni/InGaN/GaN heterostructure, grown by plasma-assisted molecular beam epitaxy, has been developed to efficiently detect acetone very rapidly at low temperature. Non-rectifying I-V characteristics of epitaxially relaxed InGaN with Ni contact have been revealed at 373 K. An incremental current of 11.74 μA has been found at 373 K with the exposure of 100 ppm of acetone vapor at an operating bias of 0.4 V. Sensitivity has been obtained from transient response curves. Most importantly, very fast response/recovery characteristics with good baseline recovery have been witnessed. The response time and recovery time have been found to be ~7.6-8.4 s and ~4.5-19.1 s. A possible explanation, including Langmuir adsorption-desorption isotherm, has also been discussed.Item Highly Sensitive Acetone Sensor Based on Pd/AlGaN/GaN Resistive Device Grown by Plasma-Assisted Molecular Beam Epitaxy(IEEE, 2017-11) Kumar, RahulHighly sensitive acetone sensing performance of Pd/AlGaN/GaN resistive devices in the temperature range of 100 °C-250 °C and in the detection range of 100-1000 ppm was reported. A plasma-assisted molecular beam epitaxy was used to grow the AlGaN/GaN heterostructure on Si (111) substrate. Structural characterization of the grown epilayers was performed through double-crystal X-ray diffraction whereas atomic force microscopy was used to obtain the roughness of the sensing surface. Resistive mode configuration of the sample was tested toward acetone in the detection range of 100-1000 ppm and in the temperature range of 100 °C-250 °C. The optimum temperature was found to be 150 °C with response magnitude ~95% for the acetone concentration of 1000 ppm. The sensor response time and recovery time were found to be in the range of ~18-44 s and ~25-109 s, respectively. The cross-sensitivity of the device with other interfering species such as butanone, benzene, toluene, and xylene attributed to good acetone selectivity of the devices. Acetone sensing as well as current transport of the Pd/AlGaN/GaN devices was illustrated with effect including Langmuir adsorption-desorption kinetics and Schottky barrier height between Pd/AlGaN interfaces.