Stable hydrogen sensors from AlGaN/GaN heterostructure diodes with TiB_2-based Ohmic contacts

摘要

The use of TiB_2-based Ohmic contacts on Pt-gate AIGaN/GaN 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 TiB_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.