The structural and electronic properties of silicene/silicane and silicene/germanene heterobilayers (HBLs) are investigated by using first-principles methods. The results show that the silicene interacts overall with silicane (germanene) with a binding energy of -50 similar to-70 meV per Si (Ge) atom, suggesting a weakly van der Waals interaction between silicene and substrate. A relative large bandgap with a linear band dispersion of HBLs is opened due to the sublattice symmetry broken by the intrinsic interface dipole between silicene and substrate. Remarkably, the band gap of all these HBLs can also be continually tuned modulated by adjusting the interlayer spacing and strain, independent on the stacking arrangements. Silicene is thus expected to be useful for building high-performance FET channel, which would extend its applicability to possible future nanoelectronics. (C) 2015 Elsevier B.V. All rights reserved.