Optical absorption and refractive index change of neutral donors in InAs/GaAs camel-like nanostructures: 3D finite element analysis

Spectral and optical properties of neutral donors confined in experimentally grown InAs/GaAs camel-like nanostructures were investigated using the spatial finite element method within the effective mass approximation. The total absorption and refractive index changes were determined by using the compact matrix density formalism. The energy spectrum was found to strongly depend on the donor’s position, with transition energies between the first three low-lying levels below 20 meV (THz band) and further tuneable by applying a static electric field along the “humps”. On-center donor, on-hump donor, and nearly single-electron systems were found to be optically active even at zero electric field. Their optical properties can also be enhanced at specific electric field strengths, a phenomenon linked to the formation of significant dipole moment values and confirmed through volumetric probability density analyses. Additionally, all the systems exhibited a periodic absorption profile with the polarization angle, resembling a “nanoscopic polarizer”.