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In GaAs nanowires grown along the cubic [111]c direction, zinc blende and wurtzite arrangements have been observed in their stacking sequence, since the energetic barriers for nucleation are typically of similar order of magnitude. It is known that the interplanar spacing of the (111)c Ga (or As) planes in the zinc blende polytype varies slightly from the wurtzite polytype. However, different values have been reported in the literature. Here, the ratio of the interplanar spacing of these polytypes is extracted based on X-ray diffraction measurements for thin GaAs nanowires with a mean diameter of 18-25 nm. The measurements are performed with a nano-focused beam which facilitates the separation of the scattering of nanowires and of parasitic growth. The interplanar spacing of the (111)c Ga (or As) planes in the wurtzite arrangement in GaAs nanowires is observed to be 0.66% ± 0.02% larger than in the zinc blende arrangement. [ABSTRACT FROM AUTHOR]

Aluminium nitride was grown on c-plane sapphire by metal organic vapor phase epitaxy (MOVPE) at temperatures of 1070°C by a pulsed growth method and in continuous growth mode at temperatures up to 1270°C. For both methods the V/III ratio was varied and different approaches for the growth start were investigated. The crystal quality was mainly characterized by scanning electron microscopy and high resolution X-ray diffraction which showed unusual line shape for certain samples. Both growth methods enabled the growth of more than thick, atomically flat, Al-polar layers with edge type dislocation densities in the order of for pulsed samples and for conventionally grown samples. [ABSTRACT FROM AUTHOR]