Temperature dependence of surface potential in a-Si : H pH-ion sensitive field effect transistor

In this study, we focus on the investigation of the relationship between th e a-Si:H/SiO2 gate pH-ion sensitive field effect transistor (pH-ISFET) and the Al/a-Si:H/SiO2 gate metal-oxide-semiconductor field effect transistor ( MOSFET). The a-Si:H thin film was deposited by plasma-enhanced chemical vap or deposition (PECVD). The thickness of the a-Si:H thin film was 1000 Angst rom. The aluminum gate electrode was deposited by a thermal evaporation sys tem. We use the Keithley 236 current-voltage (I-V) measurement system to me asure the drain-source current (I-DS) versus gate voltage (V-G) curves for the pH-ISFET and MOSFET. The surface potential of the a-Si:H sensing membra ne can be calculated from the I-DS-V-G curves of pH-ISFET and MOSFET. That is, the semiconductor related terms of threshold voltage could be eliminate d. Furthermore, we investigate the temperature dependence of the surface po tential. From experimental results, we can observe that the pH sensitivity of the surface potential is increased with increasing temperature. We can a lso find the pH(pzc) (pH at the point of zero charge) of the a-Si:H pH-ISFE T.