Response Enhancement of Pt Nanoparticles Decorated AlGaN/GaN HEMTs Treated by Photo-Electrochemical Method for Ammonia Gas Sensing at Room Temperature

In this work, we have designed an ammonia sensor based on Pt nanoparticles (NPs) decorated AlGaN/GaN high electron mobility transistors (HEMTs) operating at 300 K. The sensor was optimized by photo-electrochemical (PEC) method to achieve better ammonia gas sensing performance. And the threshold voltage of the HEMT based device was significantly positively shifted from −4.14 V to 0.32 V and the gate voltage corresponding to the maximum transconductance peak shifted from −3.60 V to 1.00 V via the PEC method. Simultaneously, PEC treatment can increase the surface-area-to-volume (S _A /V) ratio of the sensing window to enhance the ammonia gas sensing ability. The “spill-over” effect of Pt NPs provided more active sites on the surface of the sensing area. Pt NPs loaded AlGaN/GaN HEMT based sensor exhibited a relatively short response and recovery times of 29 s and 238 s, respectively, and the sensitivity increased from 0.34 % to 8.69 % towards 100 ppm ammonia when drain voltage was kept at 1.00 V at 300 K. The low limit of detection (LOD) of 20 ppm was obtained in this paper. The results showed that the studied device treated by the PEC method is indeed promising for ammonia detection in the future.