Moving towards nano-TCAD through multimillion atom quantum dot simulations matching experimental data

摘要

Low-loss optical communication requires light sources at 1.5um wavelengths.Experiments showed without much theoretical guidance that InAs/GaAs quantumdots (QDs) may be tuned to such wavelengths by adjusting the In fraction in anInxGa1-xAs strain-reducing capping layer (SRCL). In this work systematicmultimillion atom electronic structure calculations qualitatively andquantitatively explain for the first time available experimental data. The NEMO3-D simulations treat strain in a 15 million atom system and electronicstructure in a subset of ~9 million atoms using the experimentally givennominal geometries and without any further parameter adjustments thesimulations match the nonlinear behavior of experimental data very closely.With the match to experimental data and the availability of internal modelquantities significant insight can be gained through mapping to reduced ordermodels and their relative importance. We can also demonstrate that startingfrom simple models has in the past led to the wrong conclusions. The criticalnew insight presented here is that the QD changes its shape. The quantitativesimulation agreement with experiment without any material or geometry parameteradjustment in a general atomistic tool leads us to believe that the era of nanoTechnology Computer Aided Design (nano-TCAD) is approaching. NEMO 3-D will bereleased on nanoHUB.org where the community can duplicate and expand on theresults presented here through interactive simulations.