Accurate drain current modeling of long channel junctionless double-gate field effect transistor

Abstract

A new model based on linear depletion inside the channel region has been proposed for long channel Junctionless Double Gate (JL DG) MOSFETs. The proposed model shows improved performance over the previous models based on abrupt depletion. This new model provides a different way to determine surface potential of JL DG MOSFETs. The model based on gradual depletion provides different sets of equations for surface potential which are valid for different regions of operations. Thus there is a trade-off between accuracy and complexity in using the proposed model. Having the knowledge of surface potential, the proposed model obtains expressions for current and threshold voltage. The current expressions have been evaluated using numerical techniques. Surface potential characteristics and current voltage characteristics are found to have smooth transition between fully depleted region and partially depleted region. This smoothness may prove useful for SPICE like programs. Capacitance-voltage characteristics, output conductance and transconductance characteristics have also been observed, analyzed and compared against the results obtained from TCAD simulations. Upon comparison, it has been found that the results obtained from proposed model matches quite perfectly with the results provided by TCAD tool. Finally the effects of different device and process parameters on threshold voltage of the JL DG device and the sensitivities of threshold voltage on these parameters have been explored and analyzed. It has been observed that threshold voltage of JL DG MOSFET is very sensitive to parameter variations which would require proper control of geometry and impurity concentration.