Submicron-meter polycrystalline-SiGe thin-film transistors with tunneling field-effect-transistor structure

Submicron-meter polycrystalline-SiGe thin-film transistor (TFT) device with tunneling field-effect-transistor (TFET) structure has been studied. With scaling the gate length down to 1 μm, the poly-SiGe TFT device with conventional metal–oxide–semiconductor-field-effect-transistor (MOSFET) structure would be considerably degraded, which exhibits an off-state leakage of about 0.4 nA/μm at a drain bias of 3 V. The short-channel effect would tend to cause the source/drain punch-through, and also increase the lateral electric field within the channel region, thus enhancing the carried field emission via trap states. The TFET structure can be employed to alleviate the short-channel effect in poly-SiGe TFT device. As a result, even for a gate length of only 0.5 μm, the resultant poly-SiGe TFT–TFET device can exhibit good electrical characteristics with an off-state leakage smaller than 0.1 pA/μm and an on/off current ratio of about 9 orders at a drain bias of 3.0 V.