Chapter 134 AlGaN/GaN HEMT Based pH Sensor N. Sharma, S. Dhakad, K. Singh, N. Chaturvedi, A. Chauhan, C. Periasamy and N. Chaturvedi Abstract The sensitivity of GaN HEMTs upon exposure of the gate area to phosphate buffer solution (PBS) has been explored. Output drain characteristic of the device reveals that the drain current decreases linearly with pH values. Higher pH contains less H + concentration and which is tends to lower the drain current. A high sensitivity of 4.32 μA/mm-pH at V ds = +1 V is obtained. 134.1 Introduction AlGaN/GaN high-electron-mobility-transistor (HEMT) have been extremely useful for liquid sensor (pH sensor, salinity sensor), gas sensor and as a biosensor because of its remarkable properties like chemical stability, low toxicity, and superior conductivity owing to the high saturation velocity and high sheet carrier concen- tration of the two-dimensional electron gas (2DEG) layer in a AlGaN/GaN heterostructure [1]. Furthermore, pH sensors fabricated from the GaN material are mainly of great importance in chemical and biological experiments in space applications. In this paper, we are reporting on the development of GaN HEMTs based pH sensor. N. Sharma Á S. Dhakad Á K. Singh Á A. Chauhan Á N. Chaturvedi CSIR-Central Electronics Engineering Research Institute, Pilani 333031, Rajasthan, India N. Sharma Á C. Periasamy Malaviya National Institute of Technology Jaipur, Jaipur 302017, Rajasthan, India N. Chaturvedi (&) Birla Institute of Technology & Science Pilani, Pilani 333031, Rajasthan, India e-mail: nidhichatur@gmail.com © Springer Nature Switzerland AG 2019 R. K. Sharma and D. S. Rawal (eds.), The Physics of Semiconductor Devices, Springer Proceedings in Physics 215, https://doi.org/10.1007/978-3-319-97604-4_134 897