A novel micromachined uncooled infrared detector employing a-Si:H TFT as thermosensitive element

A novel micromachined uncooled infrared ( IR) detector based on hydrogened amorphous silicon (a-Si:H) thin film transistor (TFT) as thermosensitive element is proposed for the first time. It utilizes the high temperature dependence of the drain current induced by the influences of temperature variation on the effective carrier mobility in channel and on the threshold voltage. An IR resonance cavity between absorber and the gate electrode improving the IR absorptivity and a microbridge providing a low thermal conductance are designed. The differential amplifier whose input pair is two identical TFTs, of which one is shielded to the IR while the other is unshielded, can not only amplify the voltage signal that is equivalent to the drain current variation but also simultaneously compensate the self-heating effect. Using PSPICE simulator, the responsivity calculated is about 4.1mV/K at room temperature.