Comparison of transport models for a Double gate MOSFET including quantum effects. : Comparison of transport models for a Double gate MOSFET including quantum effects.

Requires: S-Pisces/Quantum
Minimum Versions: Atlas 5.28.1.R

This example demonstrates:

  • Use of the BQP model coupled with drift-diffusion and energy balance.
  • Effect of quantum confinement on carrier and current density.
  • Effect of carrier transport model on drain current of device.

In this example the drain current of a double gate MOSFET is calculated using the BQP to model quantum effects. A drift-diffusion model featuring field dependent mobility is compared with an energy balance model with an energy dependent mobility. For a device of such small dimensions as in this MOSFET, non-stationary effects will have a significant effect on the carrier transport. The energy balance model can approximate these effects, and when coupled with the BQP model it includes quantum effects too.

The first part of the deck does the calculation with energy balance (HCTE.EL on the MODELS statement) and Bohm Quantum Potential (BQP.N on the MODELS statement). FLDMOB with EVSATMOD=0 on the MODELS statement invoke an energy dependent mobility calibrated for Silicon. The NOCURRENT parameter is specified on the first SOLVE statement to directly get a solution with a gate voltage of -0.5 V. A small drain bias is applied and then the gate biases ramped to gradually turn the MOSFET on.

The second part of the deck does the same calculation using a drift-diffusion model, and with the CVT mobility model (which includes velocity saturation). The quantum effects are included by using the BQP model.

From the difference in the value of drain currents it is evident that non-stationary effects are very important. The energy balance model approximates these effects via its energy dependent mobility. By looking at the electron concentration or electron quantum potential one can see that confinement effects are similar in the two cases.

Remarks: Explicitly setting the material parameters in the oxide as done here is not strictly necessary, although it can improve convergence in some cases.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.