Low-temperature photoluminescence (PL) study of liquid phase epitaxy grown undoped and Sn doped GaIn_(0.16)As_(0.22)Sb layers lattice matched to InAs is reported. The quaternary solid solutions Ga_(1-x)In_(x)As_(y)Sb_(1-y) are promising materials for the fabrication of optoelectronics devices operating in the spectral range 3-5 μm because these alloys can form type II heterojunctions both with staggered and broken-gap alignment. The band structure engineering of these devices requires the knowledge of energy gaps and mechanism of radiative recombination transitions in the forbidden gap of cladding layers. The high quality quaternary GaIn_(0.16)As_(0.22)Sb epitaxial layers with low native defect concentration were grown lattice matched to InAs and their photoluminescence was studied at low temperatures. The emission band related to bound exciton was dominant. While the emission bands associated with the first ionization state of V_(Ga)Ga_(Sb) vacancy-antisite defect with activation energy ΔE_(A)=22meV and unknown deep defect with ΔE_(B)=46meV were found besides the main PL peak ΔE_(BE)=16meV. It was established that Sn as an amphoteric impurity can form shallow donor levels.
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