Single-crystalline gallium arsenide (GaAs) grown by various techniques can exhibit hillock defects on the surface when sub-optimal growth conditions are employed. The defects act as nonradiative recombination centers and limit solar cell performance. In this paper, we applied near-field transport imaging to study hillock defects in a GaAs thin film. On the same defects, we also performed near-field cathodoluminescence, standard cathodoluminescence, electron-backscattered diffraction, transmission electron microscopy, and energy-dispersive X-ray spectrometry. We found that the luminescence intensity around the hillock area is two orders of magnitude lower than on the area without hillock defects in the millimeter region, and the excess carrier diffusion length is degraded by at least a factor of five with significant local variation. The optical and transport properties are affected over a significantly larger region than the observed topography and crystallographic and chemical compositions associated with the defect.

A scheme of photoabsorption spectroscopy based on scanning tunneling microscopy (STM) has been developed by using a supercontinuum light as the wideband light source of a Fourier transform interferometer for spectroscopic measurements. The performance was demonstrated for a sample of GaAs. The proof-of-concept test showed that the use of the supercontinuum light instead of halogen lamps greatly enhances the signal-to-noise ratio due to the high brilliance of the supercontinuum light emitted from a small core of the photonic crystal fiber that enables tight focusing of the spectroscopy light onto the sample beneath the STM tip.

ZnSe-based heterostructures grown on GaAs substrates have been investigated for use in pin-diode LED applications. In this study, a conventional Bragg-Brentano diffractometer (BBD) has been used to screen samples for phase identification, crystallite size, presence of polycrystalline ZnSe, and initial rocking curve (RC) analysis. A limitation of the conventional diffractometer is that the smallest RC full width at half maximum (FWHM) that can be achieved is 500 to 600 arc sec. As deposition parameters are optimized and the RC limit of the conventional diffractometer is reached, analysis is moved to a four-bounce high-resolution diffractometer (HRD). Although more time for analysis is required, using the HRD has a RC resolution advantage, where RCs of <20 arc sec are obtained for neat GaAs wafers. Combining the BBD and HRD instruments for analysis of ZnSe films grown on GaAs substrates allows for an efficient means of high sample throughput combined with an accurate measurement of film alignment.

With the availability of resolution boosting and delocalization minimizing techniques, for example, spherical aberration correction and exit-plane wave function reconstruction, high-resolution transmission electron microscopy is drawing to a breakthrough with respect to the atomic-scale imaging of common semiconductor materials. In the present study, we apply a combination of these two state-of-the-art techniques to investigate lattice defects in GaAs-based heterostructures at atomic resolution. Focusing on the direct imaging of stacking faults as well as the core structure of edge and partial dislocations, the practical capabilities of both techniques are illustrated. For the first time, we apply the technique of bright-atom contrast imaging at negative spherical aberration together with an appropriate overfocus setting for the investigation of lattice defects in a semiconductor material. For these purposes, the elastic displacements associated with lattice defects in GaAs viewed along the [110] zone axis are measured from experimental images using reciprocal space strain map algorithms. Moreover, we demonstrate the benefits of the retrieval of the exit-plane wave function not only for the elimination of residual imaging artefacts but also for the proper on-line alignment of specimens during operation of the electron microscope—a basic prerequisite to obtain a fair agreement between simulated images and experimental micrographs.