Search

Growth of group-III nitrides was carried out on zirconium diboride (ZrB2) (0 0 0 1) substrates for the first time. ZrB2 is a semi-metal compound and have a hexagonal crystal structure. The a-axis lattice constant of ZrB2 is 3.169 Å, which is almost lattice-matched to GaN and AlN. GaN and AlN were grown on mirror-polished ZrB2 (0 0 0 1) substrate directly by molecular beam epitaxy using elemental Al and Ga, and radio frequency plasma-excited active nitrogen. Epitaxial growth was confirmed by in situ reflection high-energy electron diffraction observation and X-ray diffraction pole-figure measurement. The surface morphology of 1.4 μm-thick GaN layer was rough. On the other hand, that of 0.9 μm-thick AlN layer was specular. [Copyright &y& Elsevier]

Abstract: Thin (∼25nm) zincblende GaN (111) epilayers have been grown on hexagonal ZrB2 (0001) substrates by plasma-assisted molecular-beam epitaxy at temperatures near 600°C. Layers grown in near-stoichiometric conditions exhibit high phase purity; no wurtzite inclusions are detected by high-resolution X-ray diffraction or photoluminescence. For growth in the presence of excess Ga the layers are predominantly zincblende phase, but contain some wurtzite inclusions. Reducing the growth temperature to 400°C results in a much-increased fraction of wurtzite inclusions. The growth of zincblende GaN with high phase purity on hexagonal ZrB2 implies the existence of an underlying physical mechanism rather than simply a result of “growth mistakes.” A possible surface energy-related mechanism by which zincblende GaN (111) can be preferentially nucleated on hexagonal substrates is discussed. [Copyright &y& Elsevier]