Bright, stable, linearly polarized, and high-purity single-photon emitters at room temperature are observed in SiN.

III-V compound semiconductor nanowires are generally characterized by the coexistence of zincblende and wurtzite structures. So far, this polytypism has impeded the determination of the electronic properties of the metastable wurtzite phase of GaAs, which thus remain highly controversial. In an effort to obtain new insights into this topic, we cross-correlate nanoscale spectral imaging by near-field scanning optical microscopy with a transmission electron microscopy analysis of the very same polytypic GaAs nanowire dispersed onto a Si wafer. Thus, spatially resolved photoluminescence spectra could be unambiguously assigned to nanowire segments whose structure is known with lattice-resolved accuracy. An emission energy of 1.528 eV was observed from extended zincblende segments, revealing that the dispersed nanowire was under uniaxial strain presumably due to interaction with its supporting substrate. These crucial information and the emission energy obtained for extended pure wurtzite segments were used to perform envelope function calculations of zincblende quantum disks in a wurtzite matrix as well as the inverse structure. In these calculations, we varied the fundamental bandgap, the electron mass, and the band offset between zincblende and wurtzite GaAs. From this multi-parameter comparison with the experimental data, we deduced that the bandgap between the Γ 8 conduction and A valence band ranges from 1.532 to 1.539 eV in strain-free wurtzite GaAs, and estimated values of 1.507 to 1.514 eV for the Γ 7-A bandgap.

The authors report compact and chemically homogeneous In-rich InGaN layers directly grown on Si (111) by plasma-assisted molecular beam epitaxy. High structural and optical quality is evidenced by transmission electron microscopy, near-field scanning optical microscopy, and X-ray diffraction. Photoluminescence emission in the near-infrared is observed up to room temperature covering the important 1.3 and 1.55 μm telecom wavelength bands. The n-InGaN/p-Si interface is ohmic due to the absence of any insulating buffer layers. This qualitatively extends the application fields of III-nitrides and allows their integration with established Si technology.

GaAs nanowires (NWs) exhibit different, zinc blende (ZB) and wurzite (WZ), crystalline phases and one generally finds an uncontrolled switching between both phases on a scale of 1–10 nm. The change of crystalline structure and stacking fault density strongly affects the local confinement potential of GaAs NWs. Combining low temperature near-field spectroscopic imaging and transmission electron microscopy measurements performed on the very same individual GaAs nanowire allows us to gain an understanding of the local structure–property correlations in such wires. From the photoluminescence measurements at subwavelength spatial resolution local characteristics of the band structure are derived. In particular, our method enables us to assign the observed band gap reduction to the high level of impurity dopants and to distinguish emission from ZB-type regions and from periodically twinned superlattice regions. In this way we demonstrate the ability to trace spatial variations of the crystal structure along the wire axis by all-optical means. Our results provide direct and quantitative insight into the correlations between morphology and optics of GaAs nanowires and hence present an important step toward band gap engineering of nanowires by controlled crystal phase formation.