Studies on GaN-based semiconductor low cost ammonia gas sensors

• Main Author: Irfan Haziq Abdul Gani
• Other Authors: Radhakrishnan K
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/140246
• Institution: Nanyang Technological University

Gas sensing devices have been in increasing focus across industries and research in the past few decades. This project is intent on studying Gallium Nitride (GaN) based High Electron Mobility Transistors (HEMTs) for gas sensing applications, together with the properties of Two Dimensional Electron Gas (2DEG) in the HEMT operating principle and Platinum (Pt) material to functionalise the surface for Ammonia (NH3) sensing applications. Following these studies, the effect of Pt functionalisation layer thickness in AlGaN/GaN HEMT sensors on pore size is further analysed. NH3 gas sensing measurements of AlGaN/GaN HEMT based sensor devices were also conducted to observe and analyse the response and sensitivity of devices with respect to variations in concentration and temperature. Image processing was carried out on SEM images of Pt surface topology to ascertain pore size on 10 nm, 15 nm and 20 nm Pt layer thickness. Image processing was conducted with Image J software where pore areas were segmented, counted and calculated. In sensing experiments, sample devices were exposed to NH3 gas at room temperature and high temperature settings.10 nm Pt layer thickness was found to have the largest average pore size and total pore area for target gas adsorption. In sensing experiments, the device resistance increased with increasing concentrations of NH3 at room temperature. The opposite trend is observed at 275℃. The highest change of resistance is observed at 275℃ as well. It is also concluded that the sensitivity of device sensing NH3 is temperature dependent.