Modulation Effects of Hydrogen on Structure and Photoluminescence of GaN Nanowires Prepared by Plasma-Enhanced Chemical Vapor Deposition

Abstract

Gallium nitride (GaN) nanowires (NWs) were grown on Si(100) substrates at different hydrogen gas flow rates, using plasma-enhanced chemical vapor deposition. The size and morphology of the GaN NWs could be modulated by controlling the hydrogen atmosphere. The diameters of the GaN NWs ranged from 53 to 221 nm, and their morphology transformed from a hexagonal prism to a triangular pyramid upon changing the hydrogen atmosphere conditions. The modulation effects originated from the competitive equilibrium between surface and interfacial diffusion induced by hydrogen in the vapor–liquid–solid growth mechanism. The photoluminescence spectra of the different GaN NWs may have originated from two metabolic peaks, which were closely related to their nanostructures. These findings provide a simple and convenient method to modulate the structure of GaN NWs and may further the application of GaN in nano-optoelectronic devices.

Structural Modulation of GaN Nanowires Grown in High-Density Plasma Environment

“…We have made many efforts to explore the resolution of these challenges. In our previous works, we explored nonammonia methods to prepare and modulate GaN NWs with the reduction of hydrogen and activated carbon by PECVD. ,, Under the plasma-phase conditions, changing the state of the plasma in the chamber is proved to be of great help for modulating the structure of GaN NWs. ,, The plasma-phase growth environment is proved to be a potential way to modulate the structure of 1D materials widely, greenly, and rapidly …”

“…1D materials have attracted increasing attention in nano-optoelectronic devices due to their ease of integration and high specific surface areas. Various methods have been used to fabricate GaN nanowires (NWs), such as molecular beam epitaxy, pulsed laser deposition, , chemical vapor deposition (CVD), , metal oxide chemical vapor deposition (MOCVD), − and plasma-enhanced chemical vapor deposition (PECVD). , Among these methods, environmental pollution and a slow growth rate both become the main problems that result from the use of a harmful gas source (TMGa, NH 3 , and H 2 ), high growth temperature, and low reaction efficiency, which also create barriers for the structure regulation of NWs. We have made many efforts to explore the resolution of these challenges.…”

“…In addition, the liquid-phase growth mechanism is also used for the preparation of some 1D materials. Complex chemical reactions and byproducts in the liquid-phase environment are not conducive to the rapid and green growth of NWs. , Compared with the vapor and liquid phases, the plasma phase has a great advantage for 1D material growth due to its high energy and activity, such as in PECVD, microwave plasma chemical vapor deposition (MPCVD), and so on. ,, Although many fabrication experiments of GaN NWs in the plasma-phase environment have been reported, there is no relevant research on the modulation mechanism. In conventional processes, it is widely believed that the change of supersaturation at the catalyst/NW interface is an effective way to modulate the structure of NWs in the vapor- or plasma-phase environment .…”

“…17,19,20 Under the plasma-phase conditions, changing the state of the plasma in the chamber is proved to be of great help for modulating the structure of GaN NWs. 18,21,22 The plasma-phase growth environment is proved to be a potential way to modulate the structure of 1D materials widely, greenly, and rapidly. 23 Just as important, an understanding of the NW growth mechanism is necessary due to the kinetic process of modulating the structure of NWs.…”

Photoluminescence Properties of GaN Nanowires Grown in a Gradient-Plasma Environment

“…The vapor–liquid–solid (VLS) growth technique with chemical vapor deposition (CVD) is flexible and controllable to fabricate NWs . Recently, plasma-assisted CVD has been shown to be a promising method for the growth and modulation of GaN NWs. − By introducing high energy plasma phase into the growth system, the production cost can be reduced by reducing reaction temperature, replacing the harmful gas source (TMGa, NH 3 , and H 2 ) and decreasing the reaction time. In addition, due to the introduction of plasma phase, the surface energy of NW is increased, which makes the regulation of NW simpler and the controllable structure more extensive.…”