Pd gated AlGaN/GaN high electron mobility transistor for ppb level hydrogen gas detection

Abstract

With the development of fuel-cell vehicles and exhale breath diagnosis for heart failure by the detection of hydrogen (H2) gas concentration, it is urgent to lower the low limit of detection (LOD) for accurate detection. Herein, we demonstrated a Pd gated high electron mobility transistor (HEMT) based on the AlGaN/GaN multilayers structure. A critical Pd thickness as small as 2 nm was utilized to shorten the H atoms diffusion distance so that its performances in low concentrations could be improved. Indeed, the results show that our device exhibits a clear response to 50 ppb H2 with a response value of 9.6% at a moderate operating temperature of 120 °C. Ultrahigh response values are observed, for instance a response of 19,137% at 500 ppm. Moreover, the detection is fast, 2.6 s for 200 ppm H2 gas. Particularly, our device has no response to VOCs CH4 and C2H5OH, and small responses to NH3, NO2, and H2S. In addition, we also studied the effect of light illumination on the sensing performance. With blue LED illumination, the response value of the device is doubled, and the response/recovery times are significant shortened.