Dual gate architecture for high sensitivity, high selectivity chemical-sensing field effect transistors

Field effect transistors have been pursued as chemical sensors for decades because of their high sensitivity. These sensors generally fall into two categories depending on where the sensing takes place. In the “sensing semiconductor” type, the semiconducting layer is responsible for detecting the analyte. The gate electrode is isolated from the environment and a potential is applied to drive the transistor into saturation. While this configuration offers exception sensitivity, selectivity is poor. Furthermore, the detection layer must also have the ability to conduct, limiting the number of materials that can be used. This is particularly problematic for organic materials, which generally offer superior selectivity through molecular design. The other configuration, “sensing gate”, switches the positions of the gate electrode and the semiconductor so that the gate is in contact with the analyte and the semiconductor is isolated from the environment. The gate is functionalized to be sensitive to a particular analyte, which improves selectivity. However, without the ability to drive the transistor into saturation, sensitivity is tends to be poor. In this work, a dual gate field effect transistor (DG-FET) is introduced. A top gate functionalized for sensitivity to ammonia is responsible for interacting with the analyte. A second gate on the bottom of the device is used to drive the transistor into saturation to provide the sensitivity enhancement. With this configuration, the high sensitivity of the sensing semiconductor configuration is obtained in parallel with the superior selectivity of the sensing gate architecture.