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ANGEL - A Nonequilibrium Green Function Solver for LEDs
An MPI-parallelized implementation of 1-D NEGF for heterostructures. Includes off-diagonal scattering. Effective mass band structure for electrons and holes. The online tool only provides basic NEGF functionality without scattering.
Introducing ANGEL, a Nonequilibrium Green’s Function code aimed at describing LEDs.
ANGEL uses a description close to the classic NEMO-1D paper (Lake et al., JAP 81, 7845 (1997)) to model quantum transport in a light-emitting diode (LED).
ANGEL is the first 1D-heterostructure NEGF to include the coupling of electrons with a multi-mode light field to have spontaneous light emission.
Since this scattering mechanism is highly nonlocal, a diagonal scattering approximation like the one encountered in most, if not all, simulators would be invalid. ANGEL has the ability to choose how many off-diagonals are included in the scattering self-energies.
Featured scattering mechanisms are polar optical phonons, acoustic phonons, ionized impurities, a phenomenological momentum relaxation mechanism invented by Roksana Golizadeh, and the mentioned photon scattering.
This functionality requires enormous computing power, and to keep it feasible some components had to be limited to very simple descriptions. ANGEL currently implements an effective mass band structure for both electrons and holes, although it is prepared to have more sophisticated continuum Hamiltonians like the multiband k.p Hamiltionians which are so successful in optoelectronics.
ANGEL is MPI-parallelized in energy space and is a modular, highly object-oriented code to easily exchange individual components.
The Online tool only features basic NEGF functionality without scattering as of now.
ANGEL was developed by Sebastian Steiger in 2008-09 during his PhD at the Integrated Systems Laboratory, ETH Zurich.
Researchers should cite this work as follows:
- S. Steiger, R. Veprek and B. Witzigmann, "Electroluminescence from a Quantum-Well using NEGF", Proc. IWCE 2009, published by IEEE