| In recent years,quantum dot materials have received extensive attention and research due to their unique optoelectronic properties.In Ga As quantum dots are used in the preparation of semiconductor lasers,solar cells,light-emitting diodes and other optoelectronic devices because of their excellent light-emitting properties.In Ga As quantum dots are mainly prepared by molecular beam epitaxy,and their optical properties are mainly determined by factors such as density,size,distribution,and shape.The density,size,and shape of quantum dots can be adjusted by experimental conditions such as substrate temperature,deposition rate,annealing time,and arsenic pressure.The site control of quantum dots is currently mainly achieved through multi-period growth and patterned substrates.In this paper,the Ga As(001)patterned substrate was fabricated by wet etching,and In Ga As quantum dots were fabricated by droplet epitaxy and S-K mode respectively.The influence of substrate temperature,deposition rate,annealing time,patterned substrate and other growth conditions on the density,size and distribution of quantum dots was studied.(1)Firstly,Wet etching is used to prepare patterned substrate.During the etching process,the influence of etching solution formula,etching time,exposure intensity,and spin coating speed on the etching effect was studied.It is found that when the speed of spin coating is 4500r/min,the effect is the best,and the exposure intensity of 88 mj/cm-2can better transfer the prefabricated pattern to the surface of the substrate.The ratio of concentrated sulfuric acid,hydrogen peroxide and deionized water is 1:2:20 to obtain an etching solution with good etching effect.When the etching time is 15s,a patterned substrate with a channel depth of about 150nm can be obtained.(2)In As/Ga As quantum dots were prepared on the surface of Ga As(001)planar substrate using droplet epitaxy.During the experiment,the substrate temperature and deposition rate were changed and the density and morphology changes of the quantum dots were observed.It is found that as the temperature increases,the density of the quantum dots decreases,and the diameter and height of the quantum dots increase;as the deposition rate increases,the density of the quantum dots increases,and the diameter and height decrease.Combining the experimental results and the nucleation theory,the nuclear process of indium atoms on the Ga As(001)surface is analyzed in detail.The experimental phenomenon was explained through thermodynamic analysis,and the mathematical model between the nucleation density of indium atoms and the substrate temperature and deposition rate was established.(3)In Ga As quantum dots were fabricated on the surface of the patterned substrate using droplet epitaxy and S-K mode.The effects of substrate temperature,deposition rate and annealing time on the preparation of In Ga As quantum dots were analyzed.Compared with the flat substrate,the nucleation density of atoms on the surface of the patterned substrate is lower,and quantum dots are easily formed on the edge of the platform.This phenomenon is caused by the steps and defects with a higher density of the edge of the platform.The experimental results show that as the substrate temperature increases,the deposition rate decreases,and the annealing time increases,the density of quantum dots prepared by droplet epitaxy continues to decrease,and the size of quantum dots continues to increase,and the quantum dots tend to diffuse from the channel to the platform.In addition,using the S-K mode to prepare multi-period quantum dots on the surface of the patterned substrate.It is found that the density of quantum dots on the surface of the patterned substrate has increased significantly,and although the quantum dots on the edge of the platform are larger,the distribution of quantum dots is relatively uniform,indicating that multi-period growth can effectively reduce the restriction effect of the patterned substrate on the distribution of quantum dots... |
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