Control of the polarity of GaN epilayers using a Mg adsorption layer

The polarity of GaN epilayers grown by molecular beam epitaxy is controlled using Mg. This is achieved by exposing the surface to a Mg flux under growth interruption. Reflection high energy electron diffraction (RHEED) indicates the formation of Mg/sub 3/N/sub 2/. Overgrowing GaN on this surface leads to a polarity inversion either from [0001] to [000-1] or [000-1] to [0001]. The change of the polarity is followed in situ by RHEED since the surface reconstruction of GaN surface exposed to a NH/sub 3/ flux is polarity dependent: (2/spl times/2) for Ga-polarity and (1/spl times/1) for N-polarity. The polarity inversion was further confirmed by convergent beam electron diffraction. Finally, high resolution transmission electron microscopy (TEM) images show different interface morphologies between Ga/N and N/Ga polarity inversions. The control of the GaN polarity open the way for novel structures dedicated to nonlinear optics.