Characteristics of p-channel polysilicon conductivity modulated thin-film transistors

A p-channel polysilicon conductivity modulated thin-film transistor (CMTFT) is demonstrated and experimentally characterized. The transistor uses the concept of conductivity modulation in the offset region to obtain a significant reduction in on-state resistance. The conductivity modulation is achieved by injecting minority carriers (electrons) into the offset region through a diode added to the drain. Experimental results show that the conductivity modulation in the p-channel device is as effective as that in the n-channel device. This structure can provide 1.5 to 2 orders of magnitude higher on-state current than that of the conventional offset drain thin-film transistor (TFT) at drain voltage ranging from -15 V to -5 V while still maintaining low leakage current and simplicity in device operation. The p-channel CMTFT can be combined with the n-channel CMTFT to form CMOS high-voltage drivers, which is very suitable for use in fully integrated large-area electronic applications.