Enhanced oscillator strength of interband transitions in coupled Ge/Si quantum dots

We report a calculation of oscillator strength for the Delta(1)-Gamma(25)' interband transition in two vertically coupled pyramidal Ge quantum dots embedded in Si. A six-band k.p formalism was used to study the (25) hole states, and a single-band approach was used to obtain the Delta(1) electron state interacting with the hole. The elastic strain due to the lattice mismatch between Ge and Si was included into the problem via the Bir-Pikus Hamiltonian. We find that when two dots are brought closely together, the oscillator strength may enlarge by a factor of about 2 as compared to the single-dot system. (C) 2008 American Institute of Physics.