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We have studied the crystal structure of GaAs nanowhiskers grown by molecular beam epitaxy (MBE) on gold-activated GaAs(111)B substrates. The results of reflection high-energy electron diffraction and transmission electron microscopy showed that the MBE-grown GaAs nanowhiskers can form a crystal structure of sphalerite, wurtzite, or an intermediate phase close to 4H polytype, depending on the deposition conditions and the size of catalyst droplets. The results are interpreted within the framework of a thermodynamic model.

The photoluminescence properties of type II GaAs/AlAs superlattices grown on the (311) surface are determined by their polarity. Previous HRTEM investigations demonstrated a corrugation (with height of 1 nm and period of 3.2 nm) of both GaAs/AlAs and AlAs/GaAs interfaces in samples grown on the (311)A surface. In the present study, a lateral periodicity of 3.2 nm is also revealed in HRTEM images of a superlattice grown on the (311)B surface and in their Fourier transforms. However, this periodicity is poorly pronounced, which is due to fuzzy corrugation and the presence of a long-wavelength (>10 nm) disorder. Photoluminescence spectra of the GaAs/AlAs superlattice on the (311)A surface are strongly polarized relative to the direction of interface corrugation, in contrast to the (311)B superlattice, in which the corrugation is weakly pronounced. It was found that the strong mixing between the Θ and X minima of the conduction band, occurring only in sublattices with strongly corrugated interfaces, allows generation of bright red luminescence at 650 nm up to room temperature. The distinctions revealed between the superlattices grown on the (311)A and (311)B surfaces confirm that it is precisely the interface corrugation, and not crystallographic orientation, that governs the optical properties of (311) superlattices.

GaAs/AlAs superlattices grown simultaneously on GaAs substrates with the (311)A and (311)B orientations have been studied by photoluminescence and high-resolution transmission electron microscopy with a Fourier analysis of images. A periodic interface corrugation is observed for (311)B superlattices. A comparison of the structure of (311)A and (311)B superlattices indicates that the corrugation occurs in both cases and its period along the \([01\overline 1 ]\)direction is equal to 3.2 nm. The corrugation is less pronounced in (311)B superlattices, wherein it exhibits an additional modulation (long-wavelength disorder) with the characteristic lateral size exceeding 10 nm. The vertical correlation of regions rich in GaAs and AlAs, which is well observed in (311)A superlattices, is weak in (311)B superlattices due to the occurrence of long-wavelength disorder. The optical properties of (311)B superlattices are similar to those of (100) ones and differ radically from those of (311)A superlattices. As distinct from (311)B, strong photoluminescence polarization anisotropy is observed for (311)A superlattices. It is shown that it is the interface corrugation rather than the crystallographic (311) surface orientation that determines the optical properties of (311)A corrugated superlattices with thin GaAs and AlAs layers.

The structural properties of MBE-grown GaAs and Al0.3Ga0.7 As nanowhiskers were studied. The formation of wurtzite and 4H-polytype hexagonal structures with characteristic sizes of 100 nm or larger in these materials was demonstrated. It is concluded that the Au-Ga activation alloy symmetry influences the formation of the hexagonal structure.

Dichroism in the transmission of light (the dependence of the transmittance on the direction of polarization of light) is revealed in corrugated GaAs/AlAs superlattices grown on a nanofaceted A(311) surface. It is assumed that the observed effect is associated with the structural anisotropy, i.e., with the formation of an array of GaAs quantum wires. This inference is confirmed by high-resolution electron microscopy. The GaAs/AlAs superlattices containing quantum wires also exhibit polarization anisotropy of the photoluminescence observed in the yellow-red spectral range.