Green’s function-based defect identification in InAs-InAs1-xSbx strained layer superlattices

We have extended the recently developed approach that employs first-principles Hamiltonian, tight-binding Hamiltonian, and Green’s function methods to study native point defect states in InAs/InAs0.7Sb0.3 strained layer superlattices (SLS) latticed matched to GaSb. Our calculations predict a defect level at 250 meV below the GaSb valance band edge, in agreement with values deduced recently from lifetime measurements and analysis [Aytac et al. Phys. Rev. Appl., 5, 054016 (2016)]. In addition, we identify the defect level to be arising from an In-vacancy in the InAsSb region of the superlattice. The formation energy calculations further indicate that In-vacancies are easier to form in both regions of the superlattice than in bulk InAs or in InAsSb alloy. Our results suggest that In-vacancy is the most damaging native defect that limits lifetimes InAs/InAs0.7Sb0.3.