High performance ammonia gas sensor based on GaN honeycomb nanonetwork

Abstract

In this work, we have demonstrated a FET-like ammonia (NH3) gas sensor fabricated on a unique structure namely GaN honeycomb nanonetwork (GaN-HN) which is in-plane electrically conductive together with large surface-to-volume ratio. Utilizing ohmic contact Ti/Al/Ti/Au multilayers as the source and the drain terminals and Pt nanonetwork layer as the gate terminal, the FET-like NH3 gas sensors were fabricated by a two-mask photolithography process. The fabricated NH3 gas sensors have high selectivity, fast response/recovery, and a wide detection range up to 5000 ppm. The response and recovery time for 5 ppm NH3 gas are 23 s and 101 s at a moderate operating temperature of 120 °C. Interestingly, this sensor is capable to detect trace NH3 gas and the low limit of detection (LOD) is as small as 0.31 ppm. Its absorption activation energy Ea is also investigated by the transient-state study.