NEMO5: realistic and efficient NEGF simulations of GaN light-emitting diodes

The design and optimization of realistically extended multi-quantum-well GaN-based light emitting diodes requires a quantitative understanding of the quantum mechanics-dominated carrier flow. Typical devices can be characterized by spatial regions of extremely high carrier densities such as n-GaN/p-GaN layers and quantum wells coupled to each other by tunneling and thermionic emission-based quantum transport. This work develops a multi-scale model that partitions the device into different spatial regions where the high carrier domains are treated as reservoirs in local equilibrium and serve as injectors and receptors of carriers into the neighboring reservoirs through tunneling and thermionic emission. The nonequilibrium Green's function (NEGF) formalism is used to compute the dynamics (states) and the kinetics (filling of states) in the entire extended complex device. The local density of states in the whole device is computed quantum mechanically within a multi-band tight binding Hamiltonian. The model results agree with experimental I-V curves quantitatively. Our results indicate tunneling to be a major contributor to the total charge current in LEDs.