The microscopic surface structure of InP(001) is investigated by combining first-principles total-energy calculations with soft-x-ray photoelectron spectroscopy and scanning tunneling microscopy. The 4×2 cation dimer model adapted from Ga-rich GaAs(001) surfaces as well as recently proposed, rather complex 2×4 trimer reconstruction models are found to be unstable. The energetically favored 2×4 reconstructions are stabilized by dimerized In and P atoms. Unlike the well-known GaAs surface, however, mixed In-P dimers are preferred for cation-rich surfaces due to the notable size difference between the material constituents.

We report on the thorough investigation of light emitting diodes (LEDs) made of core-shell nanorods (NRs) with InGaN/GaN quantum wells (QWs) in the outer shell, which are grown on patterned substrates by metal-organic vapor phase epitaxy. The multi-bands emission of the LEDs covers nearly the whole visible region, including UV, blue, green, and orange ranges. The intensity of each emission is strongly dependent on the current density, however the LEDs demonstrate a rather low color saturation. Based on transmission electron microscopy data and comparing them with electroluminescence and photoluminescence spectra measured at different excitation powers and temperatures, we could identify the spatial origination of each of the emission bands. We show that their wavelengths and intensities are governed by different thicknesses of the QWs grown on different crystal facets of the NRs as well as corresponding polarization-induced electric fields. Also the InGaN incorporation strongly varies along the NRs, increasing at their tips and corners, which provides the red shift of emission. With increasing the current, the different QW regions are activated successively from the NR tips to the side-walls, resulting in different LED colors. Our findings can be used as a guideline to design effectively emitting multi-color NR-LEDs.

We have investigated the microscopic structure and optical anisotropy of $(2\mathrm{}\times 4)$ reconstructed GaP(001) surfaces. Optical and electron spectroscopy from GaP(001) surfaces prepared in ultrahigh-vacuum conditions were combined with first-principles calculations of the energetics and reflectance anisotropy. Symmetry, composition and surface optical anisotropy were characterized by low-energy electron diffraction, Auger electron spectroscopy, photoemission spectroscopy and reflectance anisotropy spectroscopy. In contrast to most earlier reports, we find that the stable Ga-rich surface corresponds to a $(2\mathrm{}\times 4)$ reconstruction. No $(4\mathrm{}\times 2)$ reconstruction could be observed, independent of the preparation method. Depending on the Ga coverage, however, two distinct line shapes in the reflection anisotropy spectra occur, indicating the existence of at least two different surface phases with $(2\mathrm{}\times 4)$ periodicity. This agrees with our total-energy calculations: Four $(2\mathrm{}\times 4)$ structural models may be stable depending on the chemical potentials of the surface constituents. All considered $(4\mathrm{}\times 2)$ structures, however, are unstable. Based on the comparison between calculated reflectance anisotropy spectra and measured data we suggest mixed Ga-P dimers on top of the Ga-terminated substrate as ground-state geometry for the cation-rich phase of GaP(001)$(2\mathrm{}\times 4)$. Our results indicate the formation of P dimers at the surface for the more anion-rich phase of GaP(001)$(2\mathrm{}\times 4)$.

Display technology has developed rapidly in recent years, with III–V system-based micro-light-emitting diodes (μLEDs) attracting attention as a means to overcome the physical limitations of current display systems related to their lifetime, brightness, contrast ratio, response time, and pixel size. However, for μLED displays to be successfully commercialized, their technical shortcomings need to be addressed. This review comprehensively discusses important issues associated with μLEDs, including the use of the ABC model for interpreting their behavior, size-dependent degradation mechanisms, methods for improving their efficiency, novel epitaxial structures, the development of red μLEDs, advanced transfer techniques for production, and the detection and repair of defects. Finally, industrial efforts to commercialize μLED displays are summarized. This review thus provides important insights into the potential realization of next-generation display systems based on μLEDs.