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Simulation of GaAs Nanowire Growth and Crystal Structure
摘要： Growing GaAs nanowires with well defined crystal structures is a challenging task, but may be required for the fabrication of future devices. In terms of crystal phase selection, the connection between theory and experiment is limited, leaving experimentalists with a trial and error approach to achieve the desired crystal structures. In this work, we present a modelling approach designed to provide the missing connection, combining classical nucleation theory, stochastic simulation and mass transport through the seed particle. The main input parameters for the model are the flows of the growth species and the temperature of the process, giving the simulations the same flexibility as experimental growth. The output of the model can also be directly compared to experimental observables, such as crystal structure of each bilayer throughout the length of the nanowire and the composition of the seed particle. The model thus enables for observed experimental trends to be directly explored theoretically. Here, we use the model to simulate nanowire growth with varying As flows, and our results match experimental trends with good agreement. By analysing the data from our simulation, we find theoretical explanations for these experimental results, providing new insights into how the crystal structure is affected by the experimental parameters available for growth.
关键词： Wurtzite,Zinc Blende,GaAs,Nanowire,Simulation
更新于2025-09-23 15:23:52
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Single GaAs nanowire based photodetector fabricated by dielectrophoresis
摘要： Mechanical manipulation of nanowires (NWs) for their integration in electronics is still problematic because of their reduced dimensions, risking to produce mechanical damage to the NW structure and electronic properties during the assembly process. In this regard, contactless NW manipulation based methods using non-uniform electric fields, like dielectrophoresis (DEP) are usually much softer than mechanical methods, offering a less destructive alternative for integrating nanostructures in electronic devices. Here, we report a feasible and reproducible dielectrophoretic method to assemble single GaAs NWs (with radius 35–50 nm, and lengths 3–5 μm) on conductive electrodes layout with assembly yields above 90% per site, and alignment yields of 95%. The electrical characteristics of the dielectrophoretic contact formed between a GaAs NW and conductive electrodes have been measured, observing Schottky barrier like contacts. Our results also show the fast fabrication of diodes with rectifying characteristics due to the formation of a low-resistance contact between the Ga catalytic droplet at the tip of the NW when using Al doped ZnO as electrode. The current-voltage characteristics of a single Ga-terminated GaAs NW measured in dark and under illumination exhibit a strong sensitivity to visible light under forward bias conditions (around two orders of magnitude), mainly produced by a change on the series resistance of the device.
关键词： chemical beam epitaxy,optoelectronics,dielectrophoresis,nanowire assembly,GaAs nanowire photodetector,nanofabrication
更新于2025-09-23 15:19:57
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High density GaAs nanowire arrays through substrate processing engineering
摘要： GaAs nanowires (NWs) vertically aligned were successfully fabricated through substrate processing engineering. High-density vertical GaAs NWs are grown on n-type Si (111) substrate by molecular beam epitaxy. Systematic experiments indicate that substrate pretreatment is crucial to vertical epitaxial growth of one-dimensional (1D) nanomaterials. The substrates etched using diluted buffered oxide etch (BOE) were explored to improve the NW density and vertical. We also find that the substrate processing engineering strongly affect the morphology of GaAs NWs. Finally, we demonstrate fabrication of GaAs NW arrays on Si surface by field-emission scanning electron microscopy (FE-SEM). This single-step process indeed offers a simple and cost-effective way to obtain a large area of GaAs NW arrays without using e-beam lithography (EBL) and/or nanoimprint lithography (NIL) processes. This work provided a new approach for hight density NW arrays.
关键词： GaAs nanowire arrays,self-catalyzed,buffered oxide etch,molecular beam epitaxy
更新于2025-09-09 09:28:46
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High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters
摘要： GaAs nanowire cathodes with exponential doping and graded Al composition structures are proposed for photon-enhanced thermionic emission (PETE) devices. The conversion ef?ciency models with these two nanowire cathodes are deduced on the basis of one-dimensional continuity equations. The conversion ef?ciency as a function of wire length, wire width, Al composition distribution, cathode temperature, emissive surface and back interface recombination velocity are also simulated, respectively. Results show that exponential doping and graded Al composition cathode structures can obviously improve the conversion ef?ciency of devices through introducing a built-in electric ?eld along the growth direction of nanowire. Besides, the optimum wire length and wire width range are 300–340 nm and 5.9–6.4 lm, respectively. Moreover, wider Al composition range is bene?cial to achieve higher conversion ef?ciency. These simulations provide an interesting attempt to explore the working mechanism of GaAs nano-based PETE devices and are expected to be veri?ed by the experimental results in the future.
关键词： exponential doping,graded Al composition,photon-enhanced thermionic emission,GaAs nanowire,conversion efficiency
更新于2025-09-04 15:30:14