SiGe/AsSb bilayer heterostructures: structural characteristics and tunable electronic properties

Abstract

Tunable band gap along with high carrier mobility are attractive characteristics for high speed nano electronic device applications. In this work we studied the structural and electronic properties of atomically thin silicon germanide (SiGe) and antimony arsenide (AsSb) heterobilayers using first principle calculations within density functional theory. Monolayer SiGe is a semimetal with a Dirac cone at the K point of the Brillouin zone (BZ) which combines superior properties of germanene and synthesis advantages of silicene. The study shows that a considerable band gap (90–459 meV) is introduced in SiGe when modulated by monolayer AsSb without degrading the carrier mobility. Moreover AsSb introduces negligible lattice mismatch in optimized heterobilayers which is favorable for synthesis purposes. We studied the density of states and space charge distribution to investigate the mechanism of the band gap opening and interlayer binding. Finally we modulated the band gap at K the point of the BZ efficiently by applying biaxial strain and also by changing the interlayer spacing. The calculated electron effective mass as a function of strain reveals that linear energy dispersion relation is preserved and the effective mass remains significantly small within the strained structure. The results predict that SiGe/AsSb heterobilayers can be an excellent choice in Si and Ge-based nano electronics and spintronic applications