Highly improved response and recovery characteristics of Si FET-type gas sensor using pre-bias

By adopting a new pulse pre-bias (V pre ) scheme, the response and recovery characteristics is significantly improved in Si field-effect transistor (FET)-type gas sensor having ZnO film as a sensing layer. A target gas of NO 2 , which is one of oxidizing gases, is detected by the FET-type sensor at various V pre s. It is demonstrated that a negative V pre (−3 V) improves the response by ∼2.5 times and a positive V pre (4 V) reduces the recovery time by ∼9 times in 0.5 ppm NO 2 ambience at 180 °C. The mechanism responsible for the pre-bias effect is explained using energy band diagram.