A p-channel poly-Si/Si/sub 1-x/Ge/sub x//Si sandwiched conductivity modulated thin-film transistor

A p-channel poly-Si/Si/sub 1-x/Ge/sub x//Si sandwiched conductivity modulated thin-film transistor (CMTFT) is proposed and demonstrated in this paper for the first time. This structure uses a poly-Si/Si/sub 1-x/Ge/sub x//Si sandwiched structure as the active layer to avoid the poor interface between the gate oxide and the poly-Si/sub 1-x/Ge/sub x/ material. Also an offset region placed between the channel and the drain is used to reduce the leakage current. Furthermore, the concept of conductivity modulation in the offset region is used to provide high on-state current. Results show that this structure provides high on-state current as well as low leakage current as compared to that of conventional offset drain TFTs. The on-state current of the structure is 1.3-3 orders of magnitude higher than that of a conventional offset drain TFT at a gate voltage of -24 V and drain voltage ranging from -15 to -5 V while maintaining comparable leakage current.