Comprehensive study of pseudomorphic high electron mobility transistor (pHEMT)-based hydrogen sensor

Pseudomorphic high electron mobility transistors (pHEMTs) were applied to cover an extremely wide frequency range. The pHEMT structure combined with the hydrogen sensor concept was fabricated and simulated. The remarkable saturation current density explained that the sensor was suitable for operation at room temperature. In addition, the Schottky barrier height lowered was demonstrated. From the experimental and simulated data, it was found that not only the Schottky barrier height lowering but also the change of the conduction-band discontinuity (ΔEC) in a hydrogen-containing ambience influenced the characteristics of the hydrogen sensor. The related threshold voltage change of the hydrogen sensor was also manifested. Furthermore, two important parameters of pHEMT, i.e., on-state output drain current and off-state breakdown characteristics, under exposing to a hydrogen ambience were also discussed. The studied device was shown to be a candidate for a high-power and highly sensitive hydrogen sensor and pHEMT integrated circuit applications.