A High-Sensitive Pd/InGaP transistor hydrogen sensor

In this work, the electroless plated (EP) Pd/InGaP high electron mobility transistor (HEMT) was firstly employed for hydrogen sensing. The current-voltage (I-V) characteristics under hydrogen concentrations of 5 ppm-1% and temperatures of 303-503 K were investigated. Experimentally, the Pd gate of three-terminal devices were successfully fabricated by the electroless plating method, and the studied devices exhibited excellent current-voltage characteristics with superior current control ability. For hydrogen sensing performances, the studied EP device demonstrated low detection limit, high sensitivity, and fast response. As compared with the thermal evaporated (TE) device, larger current variations can be achieved by the EP device. Even at extremely low hydrogen concentration, e.g., 4.3 ppm H₂/air, obvious current modulation was found. The maximum relative sensitivity reaches up to 428 % at a optimal gate voltage of -0.75 V. Furthermore, the transient detections showed that the sensing response was fairly fast, especially at high concentrations and high temperatures. At detection temperature of 403 K, the time for 90% response at 1 % H₂/air was within 4 seconds. These excellent sensing performances of the EP device indeed made it promising and competitive in future developments of smart hydrogen sensors integrated microelectronic systems.