An Analytical Model for the Threshold Voltage of Intrinsic Channel MOSFET Having Bulk Trap Charges

An analytical model for the bulk trap charge-induced threshold voltage variation in the intrinsic channel MOSFET is presented. A new definition of the flat band voltage, the gate voltage necessary to nullify the gate charge, which is induced by the bulk charges, is introduced. With the newly defined flat band voltage based on the bulk charge sheet approximation, the analytical MOS equations are derived for both the intrinsic channel nanowire and planar MOSFETs. It is shown that the analytical models predict the device characteristics reasonably well, compared with the numerical device simulations. Also, the error induced by the charge sheet approximation is compared with the point charge, using the numerical simulation. The model will be useful to predict the threshold voltage variation of the intrinsic poly-Si, adopted by the modern 3-D nand flash memory cell transistors.