X-ray reciprocal space maps and x-ray scattering topographic observation of GaN layer on GaAs (001) in plasma-assisted molecular beam epitaxy

Abstract

We have characterized plasma-assisted N+ molecular beam epitaxy-grown polymorphous GaN epitaxial layer on GaAs by x-ray reciprocal mapping using four-circle x-ray diffractometer and a personal computer controlled x-ray scattering topography system by ourselves. x-ray reciprocal mapping indicates that GaN wurtzite epitaxial film was grown along only [1¯1¯1] direction. While GaN wurtzite and zinc-blende crystals were contracted along the surface normal, those of lattice constants were expanded along lateral direction. The values of expansion were larger than our instrumental resolution. The lateral expansion rate of lattice constants in GaN wurtzite was larger than that in GaN zinc blende. It was found that zinc-blende phase was unevenly distributed, but wurtzite one was uniformly distributed by growth condition.