Supplementary Material

The Supplementary Material presents the DFT simulation parameters, the strain-dependent DOS, the spatial distribution of the surface and interlayer states at the G and M points, the total state density of the bilayer electrenes, the planar-averaged electrostatic potential energy, the strain-dependent thickness of the electrenes, the relative change in state density and under strain, the effect of using PAW with optB88-vdW on the layer thickness and interlayer gap of bilayer Ca2N, the phonon dispersions of monolayer Ba2N and Ba2P, the effect of vacuum spacing on the work function of monolayer Ca2N, and effect of using PBEsol on the work functions of monolayer Sr2N and Sr2P.