To understand the influence of randomly distributed donors in axial InxGa1-xN/GaN nanowire heterostructures, we have performed an elaborate statistical analysis of the electron and hole ground state confinement and recombination energies. Our simulations employ an eight-band k·p model to compute the electronic properties, fully taking elastic and piezoelectric properties into account. We assume all donors to be ionized and study their influence on electron and hole ground state by modelling them as individual point charges.
Our study reveals that randomly distributed donors induce fluctuations of the ground state transition energy of about 150 meV, almost independent of the thickness or In content of the active layer. For an ensemble, these variations translate into a broadening of the lines in photo- or electroluminescence spectra, even if all other sources of inhomogeneity such as alloy fluctuations or variations of nanowire shape and diameter or layer thickness could be eliminated. Similarly, the electron-hole ground state charge density overlap - a qualitative measure for the efficiency of light emission - shows wire-to-wire fluctuations of three orders of magnitude.
These significant wire-to-wire fluctuations of the transition energies result in broad emission bands for nanowire ensembles, but also have severe consequences for single-photon emitters based on III-nitride nanowires. Here, the presence of unintentionally incorporated donors will make it difficult to obtain reproducible transition energies and rates from nanowire to nanowire. Additionally, nanowire-based devices for the generation of entangled photons will suffer from a reduction of the overall symmetry of the system due to the presence of ionized donors.