DOCUMENTATION
Atomistic simulation with ETB: InAs QW 
TUTORIALS 
This example performs the simulation of a InAs/GaAs Quantum Well (QW) structure by employing the new Empirical Tight Binding (ETB) Module After defining an atomistic structure corresponding to the quantum cluster where we want to apply ETB calculations, we begin with continuous simulations on the whole device structure. We first perform the driftdiffusion model to get the equilibrium solution for potentials and band profiles. Then quantum ETB calculations are performed to get the electron and hole states in the QW. The device structure is defined in the geometry .geo file and is the following: In order to execute correctly this example you should have the following files in the same working directory: DEVICE STRUCTURE
In the following, some features of the input file will be described. For further details you can refer to the program reference manual. xgrowthdirection = (0, 0, 1) The regions are defined in the usual way: Region QW A cluster named Quantum is declared, to which the QW region and the two lateral barriers belong
ATOMISTIC STRUCTUREAn atomistic representation of the above defined Quantum cluster is generated by means of the Atomistic block Atomistic tb The reference region is chosen to provide the lattice parameters with which the crystalline structure is built. In this case the lattice is that of GaAs, the material composing the barrier_left region. reference_region = barrier_left In the QW region, the InAs atoms are then substituted in the lattice basis.
By default 2D periodicity is applied in yzplane orthogonal to the x growth direction of this 1D QW structure. passivation = yes
SIMULATION MODULES1. DriftdiffusionAs for driftdiffusion, as usual we define a simulation name = driftdiffusion belonging to the model driftdiffusion and associated to the whole device (deafult choice) We select a poisson calculation for an equilibrium solution: coupling = poisson The Boundary Regions for driftdiffusion are the two contact regions, defined by the two boundary surfaces anode and cathode
2. Quantum EFAFor the quantum calculations, we define an efaschroedinger simulation for kp 8x8 calculations: Module efaschroedinger The physical model is 8x8 for a k.p 4 bands calculations of electrons and holes 3. Empirical TightBindingFor the quantum calculations, we define a empirical_tb simulation, named tb: Module empirical_tb In the Module empirical_tb we define the associated regions, given by regions = Quantum ETB Hamiltonian will be created and solved based on the atomistic structure named tb which has been previously built in the Atomistic section atomistic_structure = tb Information about potential profile to be applied (due to builtin, polarization fields, etc.) is given by potential_simulation = driftdiffusion In the Solver block, we define the number of eigenstates to be calculated in valence and conduction band: num_valence_eigenvalues = 4 and we also may define a guess value for the eigensolver guess_valence = 0.5
these keywords are optionals. In this way, we avoid erroneous states due to the folding of the Hamiltonian. The reference of the guess is the valence top band edge at 0.0 eV.
Run simulationsWe may now run tiberCAD to calculate driftdiffusion ( dd simulation) for an equilibrium solution and ETB for calculation of eigenvalues of holes and electrons (tb) solve = (driftdiffusion, tb)
tibercad InAs_qw.tib ATTACHMENTS
