Systematic Study on Electronic, Mechanical, and Thermal Transport Properties of Germanium Antimony Selenide Telluride Alloy by a First-Principles Approach

Ge2Sb2Se4Te alloy has most recently exhibited its outstanding optical properties for non-volatile photonic storage applications, while its electrical and thermal transport properties were rarely reported, thus limiting its application versatility. To overcome the above issue, we performed a detailed and systematic study on the electrical, mechanical, and thermal transport properties of Ge2Sb2Se4Te alloy using first-principles calculations. The results show that Young’s modulus and shear modulus of Ge2Sb2Se4Te are anisotropic, originating from its layered crystal structure. Besides, Poisson’s ratio suggests that the in-plane bonding of Ge2Sb2Se4Te was mainly ionic-covalent bonding, while the out-of-plane bonding was of van der Waals (vdW) interaction character. The chemical bond difference between in-plane and out-of-plane directions induces strong phonon anharmonicity and phonon thermal transport anisotropy. Therefore, layered Ge2Sb2Se4Te exhibited low phonon group velocity and short phonon lifetime, resulting in encouragingly low lattice thermal conductivities of 4.45, 3.54, and 0.41 W/mK along the x-axis, y-axis, and z-axis at 300 K, respectively. Furthermore, the calculated electronic structure revealed the metallicity character of Ge2Sb2Se4Te alloy without a pronounced bandgap, which made this material applicable to thermal insulation materials rather than traditional thermoelectric materials. This work was useful to promote the application of Ge2Sb2Se4Te in the field of engineering thermal management and storage devices based on the optical-thermal mechanism.