A designing principle for low dark-current strained layer superlattices

A systematic study of native point defect states is carried out to understand the origin of gap states in strained layer superlattices. Using a combination of first principles Hamiltonian, tight-binding Hamiltonian, and Green's function approach, we calculate the native point defect states in bulk InAs, bulk GaSb, and ten InAs-GaSb strained layer superlattices. We observe that the defects in strained layer superlattices located away from the interface create fewer mid gap states if the constituent bulk materials do not have defect states in that energy interval. This can be used as a design principle to shift the superlattice band gap and reduce or eliminate the mid-gap states.