Polarity dependence of hexagonal inclusions and cubic twins in GaN/GaAs(0 0 1) epilayers measured by conventional X-ray pole figure and grazing incident diffraction pole figure

Abstract

The distribution of mixed phases and its dependence on the polarity of cubic GaN epilayers are investigated by conventional X-ray pole figure and grazing incident diffraction (GID) pole figure. The hexagonal inclusions and cubic twins can be classified into two portions: one is formed with strict crystalline orientations, the other with crystalline misorientations. The former can be measured by conventional pole figures which reveal that the density of lamellate hexagonal grains and cubic twins located on (1 1 1) Ga and ( 1 ̄ 1 ̄ 1) Ga along [1 1 ̄ 0] direction are higher than those on ( 1 ̄ 1 1) N and (1 1 ̄ 1) N along [1 1 0] direction. However, the low signals from tiny mixed phases with crystalline misorientations, detected by GID pole figures, distribute in a larger ϕ region near the [1 1 0] and [ 1 ̄ 1 ̄ 0] directions with much weaker intensity, and in a smaller ϕ region near the [1 1 ̄ 0] and [ 1 ̄ 1 0] directions with slightly stronger intensity.