Studies On The Fabrication And Optical Properties Of Ordered Si Nanocolumn Arrays/ge Quantum Dots Composite Structure

Because the motion of charge carriers in nanowires and quantum dots is restricted within nanoscale in two and three dimensions respectively,both nanowires and quantum dots exhibit many excellent optoelectronic properties.Silicon nanowires(SiNWs)are widely used as backbone materials in nano-optoelectronic and microelectronic devices for their high surface-volume ratio and efficient light absorption.In addition,with their strong quantum confinement effects and compatibility with silicon integrated circuits,germanium quantum dots(GeQDs)have also been extensively studied.Hence,the integration of SiNWs and GeQDs shows promise for application in the nano-photoelectronic and microelectronics fields.Based on nanosphere lithography(NSL),the relationship between inductively coupled plasma etching(ICP)and the size of polystyrene(PS)spheres with a diameter of 220 nm as a function of etching time and etching power is discussed.The size of the PS sphere with a diameter of 500 nm as a function of time was also discussed by reactive ion etching(RIE).It is concluded that ICP is suitable for the preparation of small-sized nanowire templates(?150 nm)due to isotropic etching and low damage.RIE is suitable for large-sized templates(>150 nm)due to its faster etching rate.The preparation,at the same time,does not damage the array structure of the template.When the nanosphere template is combined with the metal assisted chemical etching(MACE)Si nanowire,the Ag with larger catalytic activity is replaced by Au,which effectively suppresses the secondary etching of the sidewall and the top of the nanopillar and improve the smoothness of the surface of the nanopillar.In addition,in order to better realize the quantitative growth of the epitaxial film on the surface of the nanopillar,we use the a-Si film to explore the relationship between the radial increment of the nanopillar and the actual deposition amount of the substrate at different deflection angles.Thus,the conclusion that the film coating property is optimal when the deflection angle is 15° is obtained,and the coating ratio at this time is 0.277.Based on the previous coating research,we designed different thicknesses of Ge film to realize the preparation of ordered Si nanopillar array/Ge quantum dot composite structure.At the growth temperature of 700 ?,as the thickness of the Ge film increases,the density of quantum dots on the nanopillar array shows a trend of increasing first and then decreasing,while the size of quantum dots is increasing continuously and even showing a thin film growth.This is mainly due to the continual nucleation of the strain relief of the Ge layer and the tendency of coarsening,resulting in the phenomenon that the density of quantum dots is reduced due to the large island merger small island.By combining the simulation calculation with the experiment,we verified that when the ordered Si nanopillar array is combined with Ge quantum dots,it exhibits decoupling properties due to its superior performance in integrating waveguides and optical cavities.Moreover,the spontaneous emission of quantum dots is coupled with the Mie resonance of nanowires,and the phenomenon of luminescence enhancement appears.The luminescence intensity is one order of magnitude higher than that of self-organized quantum dots,and the position of the simulated enhanced luminescence peak is basically consistent with the experimental results.