Search

We realize the growth of self-catalyzedGaAsP nanowires (NWs) onsilicon (111) substrates using solid-source molecular beam epitaxy.By optimizing the V/III and P/As flux ratios, as well as the Ga flux,high-crystal-quality GaAsP NWs have been demonstrated with almostpure zinc-blende phase. Comparing the growth of GaAsP NWs with thatof the conventional GaAs NWs indicates that the incorporation of Phas significant effects on catalyst nucleation energy, and hence thenanowire morphology and crystal quality. In addition, the incorporationratio of P/As between vapor–liquid–solid NW growth andthe vapor–solid thin film growth has been compared, and thedifference between these two growth modes is explained through growthkinetics. The vapor–solid epitaxial growth of radial GaAsPshell on core GaAsP NWs is further demonstrated with room-temperatureemission at ∼710 nm. These results give valuable new informationinto the NW nucleation mechanisms and open up new perspectives forintegrating III–V nanowire photovoltaics and visible lightemitters on a silicon platform by using self-catalyzed GaAsP core–shellnanowires. [ABSTRACT FROM AUTHOR]

The growth of self-catalyzed ternarycore–shell GaAsP nanowire(NW) arrays on SiO2patterned Si(111) substrates has beendemonstrated by using solid-source molecular beam epitaxy. A high-temperaturedeoxidization step up to ∼900 °C prior to NW growth wasused to remove the native oxide and/or SiO2residue fromthe patterned holes. To initiate the growth of GaAsP NW arrays, theGa predeposition used for assisting the formation of Ga droplets inthe patterned holes, was shown to be another essential step. The effectsof the patterned-hole size on the NW morphology were also studiedand explained using a simple growth model. A lattice-matched radialGaAsP core–shell NW structure has subsequently been developedwith room-temperature photoluminescence emission around 740 nm. Theseresults open up new perspectives for integrating position-controlledIII–V NW photonic and electronic structures on a Si platform. [ABSTRACT FROM AUTHOR]

Controlled and reproducible doping is essential for nanowires (NWs) to realize their functions. However, for the widely used self-catalyzed vapor-liquid-solid (VLS) growth mode, the doping mechanism is far from clear, as the participation of the nanoscale liquid phase makes the doping environment highly complex and significantly different from that of the thin film growth. Here, the doping mechanism of self-catalyzed NWs and the influence of self-catalytic droplets on the doping process are systematically studied using beryllium (Be) doped GaAs NWs. Be atoms are found for the first time to be incorporated into NWs predominantly through the Ga droplet that is observed to be beneficial for setting up thermodynamic equilibrium at the growth front. Be dopants are thus substitutional on Ga sites and redundant Be atoms are accumulated inside the Ga droplets when NWs are saturated, leading to the change of the Ga droplet properties and causing the growth of phase-pure zincblende NWs. This study is an essential step toward the design and fabrication of nanowire devices. [ABSTRACT FROM AUTHOR]

The influences of droplet size on the growth of self-catalyzed ternary nanowires (NWs) were studied using GaAsP NWs. The size-induced Gibbs-Thomson (GT) effect makes the smaller catalytic droplets have lower effective supersaturations and hence slower nucleation rates than the larger ones. Large variation in droplet size thus led to the growth of NWs with low uniformity, while a good size uniformity of droplets resulted in the production of highly uniform NWs. Moreover, thinner NWs were observed to be richer in P, indicating that P is more resistant to the GT effect than As because of a higher chemical potential inside Ga droplets. These results provide useful information for understanding the mechanisms of self-catalyzed III-V NW nucleation and growth with the important ternary III-V material systems. [ABSTRACT FROM AUTHOR]

The III-V nanowire quantum dots (NWQDs) monolithically grown on silicon substrates, combining the advantages of both one- and zero-dimensional materials, represent one of the most promising technologies for integrating advanced III-V photonic technologies on a silicon microelectronics platform. However, there are great challenges in the fabrication of high-quality III-V NWQDs by a bottom-up approach, that is, growth by the vapor-liquid-solid method, because of the potential contamination caused by external metal catalysts and the various types of interfacial defects introduced by self-catalyzed growth. Here, we report the defect-free self-catalyzed III-V NWQDs, GaAs quantum dots in GaAsP nanowires, on a silicon substrate with pure zinc blende structure for the first time. Well-resolved excitonic emission is observed with a narrow line width. These results pave the way toward on-chip III-V quantum information and photonic devices on silicon platform. [ABSTRACT FROM AUTHOR]

We present the wafer-scale fabricationof self-catalyzed p–nhomojunction 1.7 eV GaAsP core–shell nanowire photocathodesgrown on silicon substrates by molecular beam epitaxy with the incorporationof Pt nanoparticles as hydrogen evolution cocatalysts. Under AM 1.5Gillumination, the GaAsP nanowire photocathode yielded a photocurrentdensity of 4.5 mA/cm2at 0 V versus a reversible hydrogenelectrode and a solar-to-hydrogen conversion efficiency of 0.5%, whichare much higher than the values previously reported for wafer-scaleIII–V nanowire photocathodes. In addition, GaAsP has been foundto be more resistant to photocorrosion than InGaP. These results openup a new approach to develop efficient tandem photoelectrochemicaldevices via fabricating GaAsP nanowires on a silicon platform. [ABSTRACT FROM AUTHOR]