Pulse Biasing Scheme for the Fast Recovery of FET-Type Gas Sensors for Reducing Gases

The promotive effect of a pre-bias condition on the recovery speed of a field-effect transistor-type gas sensor, which has a horizontal control gate (CG) and floating gate (FG), is investigated in this letter. To verify the pre-bias effect in the recovery phase after the detection of H
₂
S gas, a type of reducing gas, a 200-nm-thick layer of SnOx is deposited on top of the interdigitated CG and FG as a sensing material. A pulse measurement method is proposed to improve the recovery speed of the sensor for H
₂
S gas sensing by applying a negative pre-bias condition to the CG before the read operation of the sensor. This method greatly accelerates the recovery and reduces the recovery time by 74% with a pre-bias of -3 V at 180°C. The mechanism is explained in terms of energy band theory. The pre-biasing method used with our gas sensor is beneficial for the continuous monitoring and for the rapid detection of various gases.