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 mu W. Common-emitter characteristics show that the sensing base (collector) current gains at 25 degrees C in 0.01%, 0.1%, and 1% H-2/N-2 are as high as 75 (512), 134, (977), and 233 (2.89 x 10(3)), 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.