Pseudopotential study of electronic and optical properties of InAs semiconductor nanostructures

We present an atomistic pseudopotential study of the electronic and optical properties of InAs quantum dots and nanorods as a function of increasing diameter and aspect ratio. As the aspect ratio increases, energy levels cross in both conduction and valence bands, reflecting their different dependence on confinement along a specific direction. Unlike in CdSe and InP quantum rods, however, the position of the crossover between highest occupied molecular orbitals with different symmetries is found to be size-dependent and the value of the aspect ratio at the crossing to increase with the rod diameter. The level crossings at the top of the valence band are crucial to explain the evolution with elongation of all optical properties in these systems. A common monotonic behaviour of band gap, Stokes shift, degree of linear polarization and radiative lifetime, is closely linked to the variation with aspect ratio of the electronic structure of the nanocrystal valence band edge.