Investigation of AlGaN/GaN Ion-Sensitive Heterostructure Field-Effect Transistors-Based pH Sensors With Al2O3 Surface Passivation and Sensing Membrane

• Published in: IEEE sensors journal Vol. 16; no. 10; pp. 3514 - 3522
• Main Authors: Han-Yin Liu, Wei-Chou Hsu, Wei-Fan Chen, Chih-Wei Lin, Yi-Ying Li, Ching-Sung Lee, Wen-Ching Sun, Sung-Yen Wei, Sheng-Min Yu
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.05.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AlGaN/GaN; Aluminum gallium nitride; Aluminum oxide; Aluminum oxide (Al2O3); HEMTs; ion-sensitive heterostructure field-effect transistor (ISHFET); MODFETs; Passivation; pH sensor; Sensors; ultrasonic spray pyrolysis deposition (USPD); Wide band gap semiconductors; Aluminum oxide (Al2O3); ion-sensitive heterostructure field-effect transistor (ISHFET); ultrasonic spray pyrolysis deposition (USPD); pH sensor; AlGaN/GaN
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2016.2531107

This paper demonstrates an AlGaN/GaN ion-sensitive heterostructure field-effect transistors (ISHFETs)-based pH sensors with an aluminum oxide (Al 2 O 3 ) to serve as a passivation layer and a sensing membrane at the same time. Al 2 O 3 was deposited by the ultrasonic spray pyrolysis deposition (USPD) method. It was found that the ISHFET with Al 2 O 3 showed a higher pH sensitivity of 55.6 mV/pH, a faster response speed of 3 s (from pH 4 to pH 7) and 7 s (from pH 7 to pH 10), a lower hysteresis voltage of 4.3 mV, and a smaller drift rate of 1.25 mV/h (at pH 7) compared with the ISHFET without passivation. In addition, the ISHFET with an Al 2 O 3 passivation layer exhibited significant surface potential variation and low degradation rate. These results suggest that the performance of ISHFET improved using USPD-grown Al 2 O 3 .