AlGaN/GaN heterostructure pH sensor with multi-sensing segments

pH sensor is very important in various fields, and has triggered many types of devices based on different materials and mechanisms. How to improve the performances of the sensors is one of major challenges now. In the present paper, we developed an idea to improve the sensitivity of pH sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) by introducing multi-sensing segments, and experimentally fabricated prototype devicesand then investigated their responses to aqueous solutions under different pH values. The optimized sensor exhibits a very high linear sensitivity of 1.35 mA/pH at drain-source voltage of 1.5 V, which is much higher than those of conventional pH sensors with single open gate sensing area. This indicates that the multi-sensing segments is very effective in increasing the sensitivity of the pH sensor, rather than simply increasing the sensing area. The sensors degrade after measurement in solution for a long working time, but they can recover to their initial states in a certain duration after washing, typically ∼24 h. Our finding paves new strategy for the future design of high sensitive and stable pH sensors based on HEMTs.