Stable hydrogen sensors from Al Ga N ∕ Ga N heterostructure diodeswith Ti B 2 -based Ohmic contacts

• Published in: Applied physics letters 2007-06, Vol.90 (25), p.252109-252109-3
• Main Authors: Wang, Hung-Ta, Anderson, T. J., Kang, B. S., Ren, F., Li, Changzhi, Low, Zhen-Ning, Lin, Jenshan, Gila, B. P., Pearton, S. J., Osinsky, A., Dabiran, Amir
• Format: Article
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.2751107

The use of Ti B 2 -based Ohmic contacts on Pt-gate Al Ga N ∕ Ga N heterostructure diode hydrogen sensors is shown to provide very stable operation for detection of 1% H 2 in air under field conditions where temperature is allowed to vary. In contrast, the use of more conventional Ti ∕ Al ∕ Pt ∕ Au Ohmic contacts led to higher background variations in current that affect the ultimate detection threshold of the sensors. Combined with a differential pair geometry that compares current from an active diode with Pt-gate contact and a passive diode with Ti ∕ Au gate, the more stable Ti B 2 -based Ohmic contacts reduce false alarms due to ambient temperature changes. The diodes exhibit a change in forward current of more than 1 mA at 1.5 V when 1% H 2 is introduced into an air ambient.