Synthesis and Characterization of Bi/Sb-Substituted Ge-Based Equichalcogenides

The electrically/optically/thermally triggered phase-change functionality of chalcogenides in combination with exceptional IR transparency, large optical nonlinearity, photosensitivity, induced anisotropy, and ease of processing into thin films makes them perfect candidates for electronic/photonic integrated platforms. A family of new materials called equichalcogenides (containing S, Se, and Te) was shown to combine a phase-change switch effect with IR transparency and photosensitivity, making it suitable for telecommunication, phase-change non-volatile memory, and neuromorphic computation applications. In this work, the Sb in the Ge-Sb-S-Se-Te phase change material was gradually substituted with Bi, a unique dopant in chalcogenide glasses capable of changing the conduction from p- to n-type and/or creating Bi-based nanostructured regions. The possibility to create or destroy nano/micro crystallites within the initially amorphous equichalcogenide medium by external treatment allows for in-situ modification of the phase-change switching effect. The materials of the Ge₁₅Bi_xSb_40-xS₁₅Se₁₅Te₁₅ family with x = 5, 20, and 40 have been prepared and analyzed with thermal, optical, and X-ray diffraction methods.