The growth process, crystal structure, and optical properties of ultrathin GaAs and InAs wires (whiskers) as thin as 15–40 nm and about 2 μm long are reviewed and discussed. Experimental results for growing whiskers using Au as a growth catalyst during metalorganic vapor phase epitaxy (MOVPE) and the shape and growth direction of whiskers provide new insight into growth control of GaAs and InAs whiskers. The crystal structure of whiskers, Au behavior during MOVPE, and their growth mechanism are reviewed and discussed on the basis of transmission electron microscopic analysis. The photoluminescence spectra of GaAs wires are compared with those of a GaAs epitaxial layer, and the effect of surface treatment on the luminescence peak energy shift is discussed. The time dependent photoluminescence of GaAs wires is also discussed. The application of GaAs whiskers to light emitting devices is reviewed because a semiconductor wire structure employing quantum size effects is a very important element of electronic and optical devices.

We report on integration of GaAs nanowire-based light-emitting-diodes (NW-LEDs) on Si substrate by selective-area metalorganic vapor phase epitaxy. The vertically aligned GaAs/AlGaAs core-multishell nanowires with radial p-n junction and NW-LED array were directly fabricated on Si. The threshold current for electroluminescence (EL) was 0.5 mA (current density was approximately 0.4 A/cm(2)), and the EL intensity superlinearly increased with increasing current injections indicating superluminescence behavior. The technology described in this letter could help open new possibilities for monolithic- and on-chip integration of III-V NWs on Si.

We report on the formation of core-shell pn junction InP nanowires using a catalyst-free selective-area metalorganic vapor-phase epitaxy (SA-MOVPE) method. A periodically aligned dense core-shell InP nanowire array was fabricated and used in photovoltaic device applications. The device exhibited open-circuit voltage (V OC ), short-circuit current (I SC ) and fill factor (FF) levels of 0.43 V, 13.72 mA/cm 2 and 0.57, respectively, which indicated a solar power conversion efficiency of 3.37% under AM1.5G illumination. This study demonstrates that high quality core-shell structure nanowire fabrication is possible by SA-MOVPE and that the nanowire arrays can be used in integrated nanowire photovoltaic devices.

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We study the catalyst-free growth of InP nanowires using selective-area metalorganic vapor phase epitaxy (SA-MOVPE) and show that they undergo transition of crystal structures depending on the growth conditions. InP nanowires were grown on InP substrates where the mask for the template of the growth was defined. The nanowires were grown only in the opening region of the mask. It was found that uniform array of InP nanowires with hexagonal cross section and with negligible tapering were grown under two distinctive growth conditions. The nanowires grown in two different growth conditions were found to exhibit different crystal structures. It was also found that the orientation and size of hexagon were different, suggesting that the difference of the growth behavior. A model for the transition of crystal structure is presented based on the atomic arrangements and termination of InP surfaces. Photoluminescence measurement revealed that the transition took place for nanowires with diameters up to 1 microm.