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. P.Fons, H.Tampo, K.Nakahara, A.Yamada, K.Matsubara, K.Iwata, H.Takasu, S.Niki: Physica Status Solidi C, 2004, 1[4], 868-71