Hole states in vertically coupled double Ge/Si quantum dots

Abstract

Using a six-band k · p formalism we investigated the single-particle hole states in the double quantum dots made of two identical, vertically stacked, Ge/Si nanoclusters. The elastic strain due to the lattice mismatch between Ge and Si was included into the problem via Bir-Pikus Hamiltonian. As consequence of inhomogeneous strain distribution, the symmetry of states is breaking. The splitting of bonding state, σ S , from antibonding one, σ AS , is not symmetric, the average hole binding energy decreases with decreasing interdot separation. The change of interdot separation t Si causes crossing between the energy levels corresponding to σ S and σ AS orbitals. As a result, at t Si ≳ 4 nm , the antibonding state σ AS becomes the ground state of the system, replacing the σ S state.