Band-Gap Nonlinearity in Lead Chalcogenide (PbQ, Q = Te, Se, S) Alloys

[Image: see text] Narrow band-gap lead chalcogenides have been developed for several optical and electronic applications. However, band-gap energies of the ternary and quaternary alloys have received little attention compared with the parent binary phases. Here, we have fabricated single-phase ternary (PbTe)(1–x)(PbSe)(x) and quaternary (PbTe)(0.9–y)(PbSe)(0.1)(PbS)(y) and (PbTe)(0.65–z)(PbSe)(0.35)(PbS)(z) alloys and shown that although lattice parameters follow Vegard’s law as a function of composition, the band-gap energies exhibit a substantial bowing effect. The ternary (PbTe)(1–x)(PbSe)(x) system features a smaller bowing parameter predominantly due to the difference in electronegativity between Se and Te, whereas the larger bowing parameters in quaternary alloys are generated from a larger crystal lattice mismatch and larger miscibility gap. These findings can lead to further advances in tuning the band-gap and lattice parameters for optical and electronic applications of lead chalcogenides.