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.

Effect of the lattice mismatch on the efficiency of the GaAs nanowire/Si substrate solar cell

The effect of the crystal lattice mismatch between single p-GaAs nanowire grown on p-Si substrate on the solar cell efficiency is studied. The study is performed by measuring the I-V curves under red (wavelength=650 nm) laser illumination. The measurement of the single nanowire was done by conductive atomic force microscopy (C-AFM). The measured curve was reproduced by numerical simulations accounting piezoresistance and piezoelectric effects. The analysis demonstrated the presence of the tensile (2%) zinc blend insert at the interface between nanowire and substrate induced by crystal lattices mismatch. Strained insert at the interface changes the polarity of the photogenerated current and increases the efficiency by 2 times.

PULSE GROWTH OF THE GAAS NANOWIRES

The results of the simulation of the GaAs nanowire self-catalyzed growth via vapor-liquid-solid mechanism using various pulse modes are presented in this work.

Self-selective formation of ordered 1D and 2D GaBi structures on wurtzite GaAs nanowire surfaces

Scaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selective growth of ordered few atoms 1D and 2D structures. We demonstrate this concept of self-selective growth by Bi deposition and incorporation into the surfaces of GaAs NWs to form GaBi structures. Using low temperature scanning tunneling microscopy (STM), we observe the crystal structure dependent self-selective growth process, where ordered 1D GaBi atomic chains and 2D islands are alloyed into surfaces of the wurtzite (Wz) $$\{11{\bar{2}}0\}$$ { 11 2 ¯ 0 } crystal facets. The formation and lateral extension of these surface structures are controlled by the crystal structure and surface morphology uniquely found in NWs. This allows versatile high precision design of structures with predicted novel topological nature, by using the ability of NW heterostructure variations over orders of magnitude in dimensions with atomic-scale precision as well as controllably positioning in larger device structures.

Fast Response GaAs Photodetector Based on Constructing Electron Transmission Channel

Low-dimensional GaAs photodetectors have drawn a great deal of attention because of their unique absorption properties and superior responsivity. However, their slow response speed caused by surface states presents challenges. In this paper, a mixed-dimensional GaAs photodetector is fabricated utilizing a single GaAs nanowire (NW) and a GaAs 2D non-layer sheet (2DNLS). The photodetector exhibits a fast response with a rise time of ~4.7 ms and decay time of ~6.1 ms. The high-speed performance is attributed to an electron transmission channel at the interface between the GaAs NW and GaAs 2DNLS. Furthermore, the fast electron channel is confirmed by eliminating interface states via wet passivation. This work puts forward an effective way to realize a high-speed photodetector by utilizing the surface states of low-dimensional materials.

Plasmon-Enhanced Light Absorption in (p-i-n) Junction GaAs Nanowire Solar Cells: An FDTD Simulation Method Study

A finite-difference time-domain method is developed for studying the plasmon enhancement of light absorption from vertically aligned GaAs nanowire arrays decorated with Au nanoparticles. Vertically aligned GaAs nanowires with a length of 1 µm, a diameter of 100 nm and a periodicity of 165–500 nm are functionalized with Au nanoparticles with a diameter between 30 and 60 nm decorated in the sidewall of the nanowires. The results show that the metal nanoparticles can improve the absorption efficiency through their plasmonic resonances, most significantly within the near-bandgap edge of GaAs. By optimizing the nanoparticle parameters, an absorption enhancement of almost 35% at 800 nm wavelength is achieved. The latter increases the chance of generating more electron–hole pairs, which leads to an increase in the overall efficiency of the solar cell. The proposed structure emerges as a promising material combination for high-efficiency solar cells.