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Sensors 2011, 11(1), 674-695; doi:10.3390/s110100674

Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces

National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
Received: 21 December 2010 / Accepted: 6 January 2011 / Published: 11 January 2011
(This article belongs to the Special Issue Gas Sensors - 2010)
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In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C-V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C-V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C-V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I-V) characterization, suggesting that low-frequency C-V method would be effective in detecting very low hydrogen concentrations.
Keywords: GaN; AlGaN; Schottky barrier diodes; hydrogen sensors GaN; AlGaN; Schottky barrier diodes; hydrogen sensors
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Irokawa, Y. Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces. Sensors 2011, 11, 674-695.

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