We have developed a simulation for resonant tunneling diodes (RTDs) based on an empirical tight-binding model. Using the tight-binding approach allows a more careful treatment of the heterointerfaces than is possible within the more common envelope-function model. We are therefore able to take into account the effects of multiple valleys and bands in a physically meaningful way. This is particularly important for devices with barriers made of indirect bandgap materials such as AlAs.; In order to carry out these calculations, we have developed the first numerically stable transfer matrix method. With this improved method, we are able to transfer across large distances ({dollar}>{dollar}1000 A) and have for the first time included space-charge regions in a tight-binding RTD simulation.; We examine the transmission coefficients calculated with this model and discuss their features. In particular, we discuss the importance of the AlAs X-minima in devices with AlAs barriers. We also demonstrate how transverse effective-mass differences can shift the k{dollar}sbVert{dollar} {dollar}not={dollar} 0 transmission graph relative to that for k{dollar}sbVert{dollar} = 0. Finally, we present current density calculations and compare them to those made with the envelope-function model.
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