Heterojunction bipolar transistors with a planar‐type extended base as a hydrogen‐sensitive sensor

A hydrogen sensing transistor fabricated by a heterojunction bipolar transistor (HBT) with an extended base (EB) formed by a metal–semiconductor–metal (MSM) hydrogen sensor is reported. The power consumption in stand‐by mode is smaller than 2 µW. Common‐emitter characteristics show that the sensing base (collector) current gains at 25°C in 0.01%, 0.1%, and 1% H2/N2 are as high as 75 (512), 134, (977), and 233 (2.89 × 103), respectively. Low‐power consumption and high‐sensitive gains are indicative that our HBT together with planar‐type MSM sensor is very promising for applications to hydrogen sensing transistors using one voltage source.