Temperature Effect on AlN/SiO2Gate pH-Ion-Sensitive Field-Effect Transistor Devices

The temperature effect was investigated for the ion-sensitive field-effect transistor (ISFET) devices with an aluminum nitride (AlN) gate insulator. The AlN thin film was prepared on the reference electrode/electrolyte/AlN thin film/SiO 2 /p-Si substrate structure by radio frequency sputtering technology. The current–voltage characteristics of the AlN/SiO 2 gate ISFET were obtained at various temperatures and the pH sensitivities were calculated in the buffer solutions range of pH=1-11. The experimental results show that the pH sensitivities were 48.38, 52.5, 53.83, 54.46, 56.0, 56.36, and 57.25 mV/pH for 5-65±0.1°C (step 10°C). The temperature coefficient of sensitivity (T.C.S.) was determined to be 0.130 mV/pH°C. In addition, the constant voltage constant current (CVCC) readout circuit was used to measure the gate versus source output voltage in various pH buffer solutions at different ambient temperatures, which reveals the same temperature-dependent characteristics of the ISFET.