Selenium Thin Film Transistor

A new type of thin film transistor utilizing a polycrystalline Se film has been developed. An organic photoresist film is used as the gate insulating layer. The source and drain contacts have a CdSe/Au/SnO₂ structure. In this device, maximum temperature in the fabrication process is as low as 210°C, and the entire deposition process is performed by vacuum evaporations. The device exhibits enhancement-type characteristics. When V_D{=}-20 V and V_G{=}-20 V, the on-off ratio is more than 10³ and drain current about 1 μA. An enhancement/depletion type inverter is fabricated by using a device with Te/Au/SnO₂ electrodes as a depletion-type element. The current drift is discussed in terms of carrier trapping in the insulating layer.