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Large-area (3×3 mm2) flexible photodetectors were realized, based on crystalline InP semiconductor nanomembranes transferred to flexible polyethylene terephthalate substrates. Very low dark current (a few microamperes) and high responsivity (0.12 A/W) were demonstrated for flexible InP p-i-n photodetectors. Bending characteristics were also investigated for this type of flexible crystalline semiconductor photodetector, and it was found that, whereas the dark current was independent of bending radii, the photocurrent degraded, depending on the bending radii.

Low-energy electron diffraction, scanning tunneling microscopy, and photoelectron spectroscopy results from the submonolayer Sm-and Yb-induced surface structures are presented. Several similar metal-induced surface reconstructions are found to exist for Yb and Sm on Si(111)for low submonolayer coverages: 3 X 2, 5 X 1, and 7 X 1. At higher submonolayer coverage, Yb induces a 2 X 1 reconstruction while Sm induces a (&3X&3)R30'-like reconstruction. Yb is found to be divalent in all structures, whereas the Sm valence increases with increasing coverage. In the 3X2 structure only divalent Sm is present, in the 5 X 1 and 7X 1 structures a small amount of trivalent Sm appears, and, finally, in the (&3X &3)R 30 structure approximately half of the Sm atoms are trivalent. The surface Fermi-level position in the band gap for the different Sm and Yb reconstructions has been measured. The difference in valence stability between Sm and Yb is suggested to be the cause of the difference in the high-coverage structures found and the differences in pinning level for the two elements observed for the 5 X 1 and 7 X 1 structures.

Entangled photons are an integral part in quantum optics experiments and a key resource in quantum imaging, quantum communication, and photonic quantum information processing. Making this resource available on-demand has been an ongoing scientific challenge with enormous progress in recent years. Of particular interest is the potential to transmit quantum information over long distances, making photons the only reliable flying qubit. Entangled photons at the telecom C-band could be directly launched into single-mode optical fibers, enabling worldwide quantum communication via existing telecommunication infrastructure. However, the on-demand generation of entangled photons at this desired wavelength window has been elusive. Here, we show a photon pair generation efficiency of 69.9 ± 3.6% in the telecom C-band by an InAs/GaAs semiconductor quantum dot on a metamorphic buffer layer. Using a robust phonon-assisted two-photon excitation scheme we measure a maximum concurrence of 91.4 ± 3.8% and a peak fidelity to the Φ + state of 95.2 ± 1.1%, verifying on-demand generation of strongly entangled photon pairs and marking an important milestone for interfacing quantum light sources with our classical fiber networks.

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In this paper, we present the application of photoreflectance (PR) spectroscopy to investigate the energy level structure of GaInNAs-based quantum wells (QWs). Series of single GaInNAs/GaAs QWs with different nitrogen and indium contents are analysed. The electron effective mass (me*) and conduction band offset (QC) are determined and compared with the literature data. The QC in GaInNAs/GaAs system in the range of investigated GaInNAs content (28–41% of In, 0.3–5.3% of N) has been found to be almost the same as for GaInAs/GaAs system, i.e. . In addition, the energy level structure for the step-like GaInNAs/Ga(In)NAs/GaAs QWs tailored at 1.3 and 1.55 µm and the Sb-containing Ga(In)NAs/GaAs QWs is investigated. Also, the character of PR transitions, the influence of rapid thermal annealing (RTA) on the energy level structure, and the influence of the carrier localization effect on the efficiency of PR photomodulation are discussed.