5.2.3 Bias Dependence

The relative sensitivity of the three-drain MAGFET is shown in Figure 5.5 as a function of the gate voltage for different drain voltages. The simulation results show that the three-drain MAGFET has a higher relative sensitivity compared with the two-drain structure shown in the previous chapter (see Figure 4.7). A minimum relative sensitivity of 3.87 % T$^{-1}$ is obtained whereas the minimum in the two-drain MAGFET is 2.62 % T$^{-1}$.

Figure 5.5: Simulated $S_r$ as a function of the gate voltage at 300 K and -50 mT.

As described in the previous chapter, the 's' shape of the plots in Figure 5.5 can be explained in terms of how the carriers move inside the channel, diffusion or drift, as can be seen in Figure 5.6. Once again, the various minima show the transition between diffusion and drift, that means, the transition between the linear regime and the saturation regime of the MOSFET structure.

Figure 5.6: Simulated $S_r$ as a function of the drain voltage at 300 K and -50 mT.

As it was explained in the previous chapter, the gate and the drain voltages modulate the channel thickness that has a great impact on the sensor response. However, in the present analysis the relative sensitivity is a function of the polarization, because the total drains current plays an important role: the higher the drain currents, the higher the differential current although it implies a lower relative sensitivity.