Evolution of the band-gap and band-edge energies of the lattice-matched GaInAsSb/GaSb and GaInAsSb/InAs alloys as a function of composition

Using atomistic pseudopotential calculations we predict the evolution of the valence-band maximum energy E-upsilon(x,y) and conduction-band minimum energy E-c(x,y) for a compositionally graded quaternary Ga1-yInyAsxSb1-x alloy lattice matched to GaSb or InAs as a function of (x,y) or, equivalently, as a function of distance from the substrate. We find upward-concave bowing for both E-c and E-upsilon, in contradiction with simple interpolative models. A transition from staggered (type II) to broken-gap (type III) lineup relative to GaSb is predicted to occur at x=0.81 and y=0.92 on a GaSb substrate, and at x=0.59 and y=0.62 on an InAs substrate. In the latter case, the quaternary alloy has a minimum gap at x=0.85 and y=0.87.