5.7.4. Quantum Well

This tutorial is based on the following nextnano³ tutorial

• Applying the NEGF method to a quantum well

and on the following paper: [KubisNEGF2005]

The following input files were used:

• QW_InGaAs_ballistic.negf (input file for nextnano.MSB)

• QW_InGaAs_scattering.negf (input file for nextnano.MSB)

• Materials_QW_InGaAs.negf (material database for nextnano.MSB)

• 1DNEGF_InGaAs_QW_ballistic_CBR.in (input file for nextnano³, CBR method)

• 1DNEGF_InGaAs_QW_ballistic.in (input file for nextnano³, NEGF method)

• 1DNEGF_InGaAs_QW_scattering.in (input file for nextnano³, NEGF method)

• 1DNEGF_InGaAs_QW_scattering_bias.in (input file for nextnano³, NEGF method)

This example input file demonstrates how to calculate the current across a quantum well. It compares the results of a ballistic calculation to the results of a calculation including scattering. Here, input files for both nextnano.MSB and for nextnano³ are provided so that the MSB algorithm can be benchmarked against the full NEGF algorithm as implemented by T. Kubis. We use the database file called Materials_QW_InGaAs.negf where we adjusted the default material parameters so that they match the publication of [KubisNEGF2005].

Our structure consists of a 12 nm In_0.14Ga_0.86As QW in the center surrounded on each side by GaAs barriers (of width 19 nm each).

GaAs | InGaAs | GaAs

where the barrier material is indicated in bold.

Further comments regarding the MSB input file

• We used 1000 energy grid points. In contrast, the NEGF simulation used much less.

• In the database we have adjusted the material parameters, e.g. for InGaAs we used the effective mass of GaAs, the static and optical dielectric constant of GaAs and the GaAs LO phonon energy for simplicity. We use a conduction band offset of 0.150 eV.