Fig nbsp xA XRD patterns of

Before the beginning of the second stage (b), a change in the reflectance was observed, which was associated with the recrystallization processes in the GaN as well as the refractive index modulation during the temperature ramp. In contrast to the earlier processes, the growth at higher temperature (950 °C) was performed with hydrogen as the carrier gas (stage b). At this temperature, the GaN lateral growth was low but this layer was necessary to prevent the initial rapid decomposition of the GaN and exposure of the rare-earth oxide to hydrogen.