Response Comparison of Resistor- and Si FET-Type Gas Sensors on the Same Substrate

Abstract

The response characteristics of a field-effect transistor (FET)-type gas sensor are compared with those of the resistor-type gas sensor fabricated on the same Si substrate. Both types of gas sensors have the same sensing material prepared by the same process. Indium oxide (In2O3) film is adopted as a sensing material to sense NO2 gas. The two types of gas sensors have different response characteristics depending on the operating condition. The resistor-type gas sensor shows relatively constant response at all operating currents, and the Si FET-type gas sensor shows high response in the subthreshold region. Both types of sensors have the highest response at 105 degrees C, and the current of the Si FET-type gas sensor can change up to similar to 3.8 x 10(4) times at 500 ppb of NO2 gas, which is similar to 8.15 times higher than that of the resistor-type gas sensor. In addition, when the pre-bias method (V-pre = -3 V) is applied to the Si FET-type gas sensor, the response of the Si FET-type sensor overwhelm sthat of the resistor-type sensor over the entire measurement temperature and concentration range.