Characteristics of subband current ratio in double-gate MOSFET

The subband current is evaluated by solving the non-equilibrium Green's function (NEGF) self-consistently with Poisson's equation for the double-gate MOSFETs with different channel lengths and thicknesses. The characteristics of subband current ratio and the details of subband number M are simulated, and the results show that the characteristics of current are determined by the first subband when T
Si
is smaller than 2.5nm, while the value of T
Si
is between 3.5nm and 5nm, the current of the second subband needs to be considered. The subband current ratios are highly related to the gate voltage, while less sensitive to the channel length. The suitable subband number M is also discussed for the devices with different sizes, which must be considered in balancing the model accuracy and the efficiency.