Observation of direct (type-I) transitions in type-II InGaAs/AlAsSb heterostructures lattice matched to InP grown by molecular beam epitaxy

We report an optical study of heterostructures with a type-II band alignmen t that are lattice matched to InP substrates grown by molecular beam epitax y. A strong direct transition involving a confined electron and a quasiboun d hole state (both in the InGaAs layer) is observed in photoluminescence sp ectra in a low excitation regime in addition to an interface-related indire ct (type-II) transition between electrons confined in the InGaAs well and A lAsSb valence band. A direct transition between the confined electrons in t he first excited subband and valence band of InGaAs is also observed in a 2 0 nm InGaAs heterostructure in the higher excitation power regime. (C) 2000 American Vacuum Society.