GaAs Nanowires on Si Nanopillars : Towards Large Scale, Phase-engineered Arrays.

Large-scale patterning for vapor-liquid-solid growth of III-V nanowires is a challenge given the required feature size for patterning (45 to 60nm holes). In fact, arrays are traditionally manufactured using electron-beam...

Self-consistent modeling of MBE self-catalyzed GaAs nanowire growth

Self-catalyzed GaAs nanowires are synthesized by molecular beam epitaxy at various arsenic fluxes and growth temperatures. The growth of GaAs nanowires is simulated considering the kinetics of material transport inside the catalyst droplet. The re-evaporation coefficient of arsenic is estimated for the given growth conditions. Calculated nanowire growth rate is in satisfactory agreement with the experimental data.

Post-nucleation evolution of the liquid-solid interface in nanowire growth

We study using in situ transmission electron microscopy the birth of GaAs nanowires from liquid Au-Ga catalysts on amorphous substrates. Lattice-resolved observations of the starting stages of growth are reported here for the first time. It reveals how the initial nanostructure evolves into a nanowire growing in a zincblende <111> or the equivalent wurtzite <0001> direction. This growth direction(s) is what is typically observed in most III-V and II-VI nanowires. However, the reason for this preferential nanowire growth along this direction is still a dilemma. Based on the videos recorded shortly after the nucleation of nanowires, we argue that the lower catalyst droplet-nanowire interface energy of the {111} facet when zincblende (or the equivalent {0001} facet in wurtzite) is the reason for this direction selectivity in nanowires.

High electron mobility in strained GaAs nanowires

Transistor concepts based on semiconductor nanowires promise high performance, lower energy consumption and better integrability in various platforms in nanoscale dimensions. Concerning the intrinsic transport properties of electrons in nanowires, relatively high mobility values that approach those in bulk crystals have been obtained only in core/shell heterostructures, where electrons are spatially confined inside the core. Here, it is demonstrated that the strain in lattice-mismatched core/shell nanowires can affect the effective mass of electrons in a way that boosts their mobility to distinct levels. Specifically, electrons inside the hydrostatically tensile-strained gallium arsenide core of nanowires with a thick indium aluminium arsenide shell exhibit mobility values 30–50 % higher than in equivalent unstrained nanowires or bulk crystals, as measured at room temperature. With such an enhancement of electron mobility, strained gallium arsenide nanowires emerge as a unique means for the advancement of transistor technology.

Effect of Au substrate and coating on the lasing characteristics of GaAs nanowires

Optically pumped lasing from highly Zn-doped GaAs nanowires lying on an Au film substrate and from Au-coated nanowires has been demonstrated up to room temperature. The conically shaped GaAs nanowires were first coated with a 5 nm thick Al2O3 shell to suppress atmospheric oxidation and band-bending effects. Doping with a high Zn concentration increases both the radiative efficiency and the material gain and leads to lasing up to room temperature. A detailed analysis of the observed lasing behavior, using finite-difference time domain simulations, reveals that the lasing occurs from low loss hybrid modes with predominately photonic character combined with electric field enhancement effects. Achieving low loss lasing from NWs on an Au film and from Au coated nanowires opens new prospects for on-chip integration of nanolasers with new functionalities including electro-optical modulation, conductive shielding, and polarization control.