An investigation was made of the effect of in situ annealing and N doping upon 40nm low-temperature buffer layers in radical-source molecular beam epitaxy, as well as subsequent high-temperature ZnO layers grown onto the buffers. All of the layers were grown onto (11▪0) sapphire substrates. High-resolution X-ray reciprocal space maps in the vicinity of the ZnO (00▪2) reciprocal lattice point exhibited a sharp reduction in diffuse scattering for the thermally annealed buffer layer; thus implying a reduction in dislocation density. The X-ray lateral coherence values obtained from asymmetrical diffraction near to the (10▪4) reciprocal lattice point indicated that the lateral coherence of an undoped high-temperature ZnO layer grown onto an in situ N-doped buffer was larger than those of high-temperature ZnO layers grown onto either in situ annealed or untreated low-temperature buffers. The increased lateral coherence was found to be related to in-plane twisting; thus suggesting that dislocation bunching might be present at domain boundaries in high-temperature ZnO grown onto annealed N-doped buffer layers.

Thermal Processing Induced Structural Changes in ZnO Films Grown on (1120) Sapphire Substrates using Molecular Beam Epitaxy. Fons, P., Tampo, H., Nakahara, K., Yamada, A., Matsubara, K., Iwata, K., Takasu, H., Niki, S.: Physica Status Solidi C, 2004, 1[4], 868-71