Study On The Diffusion Behavior Of Al Droplets On GaAs Surface

Nano-scale metal architectures are paying more and more attention in the fields of electronics,due to the unique electromagnetic and physicochemical properties,such as Micro-Electro-Mechanical System?MEMS?devices,diagnostics,biosensing,spectroscopy,and microscopy.Among different self-assembled epitaxial growth methods,the obvious advantage of droplet epitaxial growth is its flexibility,because it is suitable for both lattice mismatched systems and lattice matched systems.Since the initial work of Koguchi et al,various point-shaped,ring-shaped,and hole-shaped nanostructures have been observed on group III-V semiconductors.Most of the previously published work involves the formation of nanostructures from gallium?Ga?or indium?In?droplets.Studies on the diffusion behavior of aluminum droplets are rarely reported.The research on the nanostructures formed during the diffusion process will not only richen our knowledge of group III droplet epitaxy and help to understand the mechanism of droplet epitaxial growth.Aluminum is the most chemically reactive element in group III metals,so it will also have a corresponding unique nanostructure.In this paper,the controlled variable method is used to investigate the diffusion behavior of aluminum droplets on the GaAs surface by changing one of the conditions: placement time,arsenic pressure,substrate temperature,and source deposition rate.The main results of this paper are the following:?1?Study on the change of aluminum droplet morphology by changing the placing time?0 s,120 s,300 s,420 s,600 s?under zero arsenic pressure,with other conditions keep constant.After analysis using the calculation results and experimental results,it is found that the droplet ripening and diffusion behavior reaches a balance at t=239 s,and t=575 s is the total time required for droplet consumption.At this time,the droplet height decreases,and the aluminum droplet outer lateral diffusion is transformed into etching the substrate downward;?2?Study on the change of aluminum droplet morphology by changing the substrate temperature?480 ?,510 ?,540 ??,with other conditions keep constant.As the substrate temperature increases,the droplet density gradually decreases,while the droplet size and height gradually increase.It is also found that the ratio of droplet liquid diameter and height decreases with increasing temperature,which indicates that the substrate temperature has a greater influence on the diffusion of aluminum droplets in the plane than the anisotropy of droplet diffusion;?3?Study on the change of aluminum droplet morphology by changing the deposition rate?0.1 ML/s,0.17 ML/s,0.3 ML/s?,with other conditions keep constant.The morphology of aluminum droplets was observed,and the droplet nucleation process was analyzed in detail.In the case of a certain deposition amount,the droplet density increases with the increase of the deposition rate,and the size decreases with the increase of the deposition rate.Combining the influence of the substrate temperature on the formation of aluminum droplets,the specific relationship between the density of aluminum droplets and the substrate temperature and droplet deposition rate is obtained by fitting the relationship curve:n_x=0.385×R^0.636×exp(2.58×10^-19/kT).