Title: Effects of various functionalisation layers on ammonia gas sensing using AlGaN/GaN high electron mobility transistors

Authors: A. Ranjan; M. Agrawal; K. Radhakrishnan; N. Dharmarasu

Addresses: Center for Micro/Nano-Electronics (NOVITAS), School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore ' Center for Micro/Nano-Electronics (NOVITAS), School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore; Temasek Laboratories@NTU, Nanyang Technological University, 637553, Singapore ' Center for Micro/Nano-Electronics (NOVITAS), School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore; Temasek Laboratories@NTU, Nanyang Technological University, 637553, Singapore ' Temasek Laboratories@NTU, Nanyang Technological University, 637553, Singapore

Abstract: Low concentration (<50 ppm) sensing of NH₃ over a wide temperature range of 30-275°C using AlGaN/GaN high electron mobility transistor (HEMT) based gas sensors with Pt, Pd and Ag functionalisation layers has been studied. Pt/AlGaN/GaN HEMT exhibited the sensitivity of 0.51% and 0.83% for 50 ppm NH₃ at 30°C and 275°C, respectively. The current decreased when the sensor was exposed to different concentrations of NH₃ at 30°C while it increased above 200°C. The sensing mechanisms corresponding to the temperature dependent response of NH₃ have been explained. The sensor with the Pd functionalisation layer exhibited higher sensitivity at 275°C as compared to Pt and Ag sensors due to higher hydrogen affinity of Pd. The sensor with the Ag functionalisation layer demonstrated faster response and recovery times (<3 min) as compared to other sensors using Pt and Pd.

Keywords: AlGaN/GaN HEMT; NH₃; Pt; Pd; Ag; functionalisation layer; gas sensor.

DOI: 10.1504/IJNT.2020.109347

International Journal of Nanotechnology, 2020 Vol.17 No.1, pp.16 - 28

Published online: 03 Sep 2020 *

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