Electronic and optical properties of dilute nitrogen quantum dots

A theoretical study of the electronic and optical properties of the dilute-nitrogen InGaAsN/GaAs quantum dot (QD) structures is presented. The calculations are based on a 10 band k middot p band-anti-crossing Hamiltonian incorporating valence, conduction and nitrogen-induced bands. Numerical results for the model system of capped pyramid-shaped QD with [1 0 1] facets on a thin wetting layer are presented. The analysis shows that the influence of nitrogen induces more confined states in the conduction band (CB) than in equivalent nitrogen-free QDs, reducing the energy of the fundamental optical transition. The better confinement in dilute nitrogen QD is because of both the significantly reduced compressive strain, which was one of the major obstacles for a long-wavelength emission from InAs/GaAs QDs, and the BAC effect. These effects, in conjunction with QD size variation, can be of great benefit for the design of devices emitting at longer wavelengths. Furthermore, in contrast to nitrogen-free QDs, dilute nitrogen QDs exhibit reduced dipole matrix element and larger Coulomb interaction energy. The findings are in good agreement with the reported experimental results on similar structures. With appropriate tailoring of the indium and nitrogen concentration, this system could be a potential candidate for a 1.55 mum emission on GaAs substrate