Optical properties and conductivity of biased GaAs quantum dots

Abstract

We report the intraband optical absorption influence on the tunneling currents in biased gallium arsenide quantum dots. The energy levels and tunneling times are calculated using a complex eigenvalue formalism through an axisymmetrical two-dimensional finite element method. The absorption coefficient and the relative change of the refractive index are evaluated by taking into account a variable intraband relaxation time. A field-invariable relaxation, as it was often assumed by previous theoretical models, cannot be justifiable even for moderate electric fields. On the one hand, our work shows that the electron escape probability and implicitly the tunneling current may be controlled by the resonant optical field. Optically switching the QDs from lower to higher conductivity states is shown to be feasible. On the other hand, at high values of the electric field the tunneling-related electronic linewidth broadening blue-shifts and enlarges the absorption peaks, thus reducing the resonant nature of the intraband transitions.