H₂S gas sensing properties in polysilicon control-gate FET-type gas sensor

H₂S gas sensing characteristics of a polysilicon control-gate (CG) FET-type gas sensor are investigated. The 15 nm thick In₂O₃ deposited using a radio frequency magnetron sputtering method is used as the sensing material. The metal CG is modified to poly-silicon CG, and the gas sensor with polysilicon control-gate operates well without any problems. The modified FET-type gas sensor has two CG terminals (V_CG1 and V_CG2), and the gas sensor with opened V_CG2 shows better gas sensing characteristics by means of higher transconductance (g_m) than gas sensor with grounded V_CG2. H₂S gas sensing characteristics are examined while varying the operating temperature, the concentration of the H₂S gas, and the pre-bias voltage (V_pre). The sensing mechanism for detecting the H₂S gas in an FET-type gas sensor is examined. The polysilicon control-gate FET-type gas sensor is able to detect up to 5 ppm of H₂S gas. The FET-type gas sensor shows significantly improved gas response by using the pre-bias scheme.