Except where otherwise noted, all materials were used as received, including potassium hydroxide pellets (KOH, Macron Chemicals, ACS 88%), boric acid (H 3 BO 3 , Sigma-Aldrich, BioReagent ≥99.5%), potassium ferrocyanide trihydrate (K 4 Fe(CN) 6 • 3H 2 O, Acros, >99%), potassium ferricyanide (K 3 Fe(CN) 6 , Fisher Chemicals, certified ACS 99.4%), potassium chloride (KCl, Macron Chemicals, Granular ACS 99.6%), Br 2 (Sigma Aldrich, 99.999%), and CH 3 OH (EMD Millipore, >99.9%). Water with a resistivity of 18.2 MΩ•cm was obtained from a Millipore deionized water system. Single-side polished, Sn-doped (N d = 4.22-5.83×10 17 cm -3 ), (100)oriented, n-type InP wafers were obtained from AXT Inc. Nominally undoped (N d = 10 15 cm -3 ), (100)-oriented, n-type single-side-polished InP wafers were obtained from MTI Inc. Zn-doped (N a = 3×10 18 cm -3 ), (100)-oriented, p-type single-side-polished InP wafers were obtained from MTI Inc. Growth of the p + n-InP junction:All samples were grown on InP (001) epi-ready substrates in a Varian Gen-II Molecular-Beam Epitaxy (MBE) system that had been modified to thermally crack gas-phase PH 3 to P 2 and H 2 .Elemental In and Be were used as group-III and p-type sources, respectively. At ~410 °C, the native oxide on the substrate surface was fully desorbed under the P 2 overpressure, as confirmed by streaky 2×4 surface reconstruction patterns observed using reflection high-energy electron diffraction (RHEED). The highly doped p + -InP layer growth was triggered when the In shutter was opened and the InP film growth rate was set at 1 μm h -1 (i.e., 1 monolayer s -1 ), as calibrated by the RHEED oscillations. The PH 3 flow rate was set at 6 sccm throughout the growth. The doping for these two samples was ~5×10 18 cm -3 , as calibrated by Hall measurements on InP test film samples grown on semi-insulating InP substrates. A p + -layer with a thickness of 100 nm was

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Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on a Si substrate by molecular beam epitaxy are examined using a variety of optical characterization techniques, including cw- and time-resolved photoluminescence and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated based on the observation of intense emission from a single NW at room temperature. This emission is shown to originate from radiative transitions within N-related localized states. From ODMR, growth of GaP/GaNP NWs is also found to facilitate formation of complex defects containing a P atom at its core that act as centers of competing non-radiative recombination.

Measurements demonstrate control over retinal neural activity both by light and electrical bias, validating the feasibility of the proposed architecture and its system components as an important first step towards a high-resolution optically addressed retinal prosthesis.

The III–V semiconductor nanowires (NWs) have a great potential for applications in a variety of future electronic and photonic devices with enhanced functionality. In this work, we employ polarization-resolved microphotoluminescence (μ-PL) spectroscopy to study polarization properties of light emissions from individual GaNP and GaP/GaNP core/shell NWs with average diameters ranging between 100 and 350 nm. We show that the near-band-edge emission, which originates from the GaNP regions of the NWs, is strongly polarized (up to 60% at 150 K) in the direction perpendicular to the NW axis. The polarization anisotropy can be retained up to room temperature. This polarization behavior, which is unusual for zinc blende NWs, is attributed to local strain in the vicinity of the N-related centers participating in the radiative recombination and to preferential alignment of their principal axis along the growth direction. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to tailor the polarization anisotropy of III–V nanowires, which is advantageous for their applications as nanoscale emitters of polarized light.