Electronic structures of (In,Ga)As/GaAs quantum dot molecules made of dots with dissimilar sizes

Using single-particle pseudopotential and many-particle configuration interaction methods, we compare various physical quantities of (In,Ga)As/GaAS quantum dot molecules (QDM's) made of dissimilar dots (heteropolar QDM's) with QDM's made of identical dots (homopolar QDM's). The calculations show that the electronic structures of hetero-QDM's and homo-QDM's differ significantly at large interdot distance. In particular, (i) unlike those of homo-QDM's, the single-particle molecular orbitals of hetero-QDM's convert to dot-localized orbitals at large interdot distance. (ii) Consequently, in a hetero-QMD the bonding-antibonding splitting of molecular orbitals at large interdot distance is significantly larger than the electron hopping energy whereas for a homo-QDM, the bonding-antibonding splitting is very similar to the hopping energy. (iii) The asymmetry of the QDM increases significantly the double occupation for the two-electron ground states and therefore lowers the degree of entanglement of the two electrons.