Facet-Dependent Properties of Mercury Telluride for Infrared Optoelectronics

Abstract HgTe is a highly tunable narrow-gap semimetal with applications to infrared optoelectronics, terahertz photodetection, and topological insulators, yet the connection between surface orientation, reconstruction, thermodynamic stability, and electronic self-passivation remains poorly understood. Here, we combine first-principles density functional theory calculations with ab initio thermodynamics to compare the low-index (100), (110), and (111) facets of zincblende HgTe across Hg-rich and Te-rich limits. We find that the nonpolar stoichiometric HgTe(110) facet is uniquely favorable, exhibiting the lowest surface energy (∼0.26 J m–2) and a pronounced cation-in/anion-out reconstruction that nearly restores bulk-like bonding and removes dangling bond states at the Fermi level. Calculated work functions span 3.10–6.09 eV, demonstrating strong facet and termination dependence relevant to band alignment and contact design. Together, these results identify HgTe(110) as an intrinsically stable, electronically self-passivated facet and provide insight into HgTe interfaces in thin-film and quantum dot optoelectronic devices.