Unconventional carrier polarity and conductivity control by ion-substitution-induced structural and defect modulation in layered Sn-based chalcogenides

Abstract Control of carrier polarity and concentration is essential for achieving high-performance semiconductor devices. Although carrier doping is conventionally realized by aliovalent ion substitution, this approach is sometimes ineffective. This review highlights unconventional ion substitution effects and novel carrier-doping mechanisms in layered Sn-based mono-chalcogenides. Double switching of charge polarity is realized in Sb-doped SnSe, where the dominant Sb substitution site changes from Se to Sn with increasing Sb content, and the associated formation of impurity bands alters the carrier type. Isovalent Te-doped Sn(Se 1− x Te x ) enhances p-type conductivity by promoting the formation of hole-donating Sn vacancies through weak Sn–Te bond formation. In contrast, isovalent Pb-doped (Sn 1− x Pb x )S enables high-density n-type doping through Pb 2+ /Sn 2+ intercalation in the interlayer space. Furthermore, 10 5 -fold modulation of electronic conductivity is induced by the reversible transition between layered and cubic structures in (Sn 1− x Pb x )Se. These findings open new avenues for designing functional semiconductors through ion-substitution-induced structural and defect modulations.