Blocking growth by an electrically active subsurface layer: The effect of si as an antisurfactant in the growth of GaN

Combining aberration corrected high resolution transmission electron microscopy and density functional theory calculations we propose an explanation of the antisurfactant effect of Si in GaN growth. We identify the atomic structure of a Si delta-doped layer (commonly called SiNx mask) as a SiGaN3 monolayer that resembles a sqrt(3) x sqrt(3) R30 surface reconstruction containing one Si atom, one Ga atom, and a Ga vacancy (VGa) in its unit cell. Our density functional theory calculations show that GaN growth on top of this SiGaN3 layer is inhibited by forming an energetically unfavorable electrical dipole moment that increases with layer thickness and that is caused by charge transfer between cation dangling bonds at the surface to VGa bound at subsurface sites.