Study on the temperature effects of Al2O3 gate pH-ISFET

In this paper, we study on the temperature effect of the commercial Sentron 1090 Al2O3 gate pH-ISFET and compare with that of the a-Si:H gate pH-ISFET, which was fabricated by our laboratory. In our experiments, we immersed the Sentron 1090 Al2O3 gate pH-ISFET into the buffer solution at the various temperatures from 15 to 55 °C. The Keithley 236 Semiconductor Parameter Analyzer was used to measure the drain-source current (IDS) versus gate voltage (VG) curves at pH=1, 3, 5, 7, 9, 11, 13 (a-Si:H gate pH-ISFET at the pH range from 1 to 7). From the IDS versus VG curves, we obtained the temperature coefficient (TC) of the Sentron 1090 Al2O3 gate pH-ISFET. We also observed the IDS0 of the Sentron 1090 Al2O3 gate pH-ISFET and a-Si:H gate pH-ISFET, where IDS0 was the operation current IDS for zero temperature coefficient. When IDS is greater than IDS0, the temperature coefficient is positive. When IDS is less than IDS0, the temperature coefficient is negative. Furthermore, we also found that IDS0 is inversely proportional to the pH value of the buffer solution, and the temperature coefficient is proportional to the pH value of the buffer solution.