A pH sensor using Gallium Nitide based semiconductor with gateless field effect transistor type structure

Abstract

GaN-based wide bandgap semiconductors have become one of the most extensively studied materials and rapid progress has been demonstrated in both optical and electronic devices. Due to their wide bandgap, good thermal and chemical stability, GaN-based semiconductor materials are also very promising for high temperature pH sensor devices. The purpose of this project is to fabricate GaN based pH sensor and characterize the sensing characteristics with different pH values. This project is mainly concerned on fabricating the pH sensor using n- AlGaN/GaN HEMT with gateless FET structure. The sensor must have high performance for Intelligent Quantum (IQ) chip application in order to follow the circulation of epoch. IQ chip is required to develop a new device for Ubiquitous Network Society (UNS). It is a smart chip with nanometer scale quantum processors and memories are integrated on chip with capabilities of wireless communication, wireless power supply and various sensing functions. The discussion in this project report focuses on the device and material structure of fabricated sensor, the fabrication process, the measurement setup and the results of device characterization and measurement. Based on results obtained, the FET behavior was observed from the IDS vs. VDS of device fabricated. The potential of the AlGaN surface at the sensing area can be effectively controlled by the solution. Thus, good gate controllability was observed. Moreover, it was observed in that current collapse normally in AlGaN based FET device. From the experiment, the drain-source current decreases with the pH level as expected. Therefore, it can be concluded that the gateless AlGaN/GaN HEMTs shows significant change in current as exposure to different pH solutions.