研究目的
Investigating the growth of horizontal GaN nanowires on silicon (111) substrate and the effects of catalyst migration and coalescence on their growth.
研究成果
The study successfully demonstrated the growth of horizontal GaN NWs on silicon (111) using SVLS growth, revealing the significant impact of catalyst migration and coalescence on NW growth. The NWs exhibited single crystalline structures and good optical properties, indicating potential for highly integrated III?V nanodevices on silicon. The findings provide insights into controlling NW growth for future nanodevice applications.
研究不足
The study is limited by the technical constraints of the HVPE growth process and the potential for optimization in controlling catalyst migration and coalescence for more uniform NW growth.
1：Experimental Design and Method Selection:
Horizontal GaN NWs were grown on silicon (111) by a surface-directed vapour–liquid–solid (SVLS) growth method using Au/Ni catalysts. The growth process was conducted in a homemade horizontal HVPE reactor at atmospheric pressure, heated by a three-zone furnace.
2：Sample Selection and Data Sources:
Silicon (111) substrates were used, with some comparisons made using sapphire (C-plane, R-plane), and GaN (0001) substrates. The native oxide on silicon was removed by rinsing in a HF-H2O solution before deposition of a 4 nm-thick Au/Ni film by electron beam evaporation.
3：List of Experimental Equipment and Materials:
Equipment includes a homemade horizontal HVPE reactor, electron beam evaporator, scanning electron microscopy (FESEM, Hitachi 4800), atomic force microscope (AFM), high-resolution transmission electron microscopy (HRTEM, FEI Tecnai F30 at 300 KV), focused-ion beam (FIB), electron dispersive spectroscopy (EDS), micro-photoluminescence (μ-PL), and cathodoluminescence (CL) measurement systems.
4：Experimental Procedures and Operational Workflow:
GaN NWs were grown by flipping the substrates and adding supports between the tray and the substrate to allow gas diffusion. The growth process involved forming GaCl gas in a reaction between liquid gallium and gaseous HCl at 850℃, mixing with NH3 in the second zone, and maintaining the temperature at 980℃ for NWs growth in the third zone.
5：Data Analysis Methods:
The morphology of the GaN NWs was characterized by SEM and AFM. HRTEM and SAED were used to analyze the NW structure and material quality. EDS, μ-PL, and CL measurements were performed to analyze the NWs chemical composition and optical properties.
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