Preparation Of Highly Symmetrical GaAs Quantum Dot Quantum Light Source

As a new research field,quantum communication combines information theory with quantum theory to form a new way of information transmission relying on quantum entanglement effect.Semiconductor quantum dots have gradually become the best source of indistinguishable single photon,which is the main candidate of entangled light source in the future quantum technology.In this paper,MBE technology is used to fabricate high symmetry Ga As quantum dot entangled light source.Firstly,the effects of surface reconstruction and growth conditions at different temperatures on the quality of Al Ga As films were studied.The relationship between surface reconstruction and temperature in Al Ga As / Ga As heteroepitaxy was explored by high energy electron diffraction(RHEED).Combined with the energy band structure and luminescence mechanism of Al Ga As and Ga As,the influence of Al content in Al Ga As on the luminescence in Ga As quantum dots prepared by droplet etching method was revealed,and the growth conditions and the range of Al composition of Al Ga As in droplet etching method were established.Then the highly symmetrical Ga As quantum dots were prepared.The deposition amount and deposition rate of Ga As quantum dots were optimized,and the quantum dots with light intensity of 6W were obtained.The fine structure splitting is reduced from two aspects of QD growth:(1)the droplet etching method avoids the fine structure splitting caused by lattice mismatch stress.(2)By growing quantum dots in nanopores,the shape of quantum dots is limited.The optical properties of QDs were characterized,the PL spectra of the double exciton cascade emission were measured,and the fine structure splitting of QDs was measured.Quantum dots at different wavelengths(700nm and 770nm)were found.Because the entangled light source of Ga As quantum dots prepared by droplet etching still has a small fine structure splitting,according to the causes of fine structure splitting,the preparation of nanoholes is systematically and comprehensively studied and analyzed.Through the analysis of droplet etching mechanism,the growth conditions that affect the shape of nanopores are mainly divided into droplet and annealing.(1)The epitaxial growth conditions such as deposition amount,deposition rate and deposition temperature of Al droplets were optimized.It was found that the droplets formed on Al Ga As were asymmetric due to Ostwald ripening and As pressure,which affected the symmetry of nanopores.(2)The etching conditions of annealing temperature,time and as pressure were optimized.The results show that the symmetry of the nanopores after annealing is better than that before annealing.However,it is found that Ga As quantum dots still have fine structure splitting.The reason for the splitting is the different inclination of the nanoholes.Combined with band structure,entanglement and experimental results,new requirements for the preparation of nanopores are proposed.The research optimizes the preparation of highly symmetric Ga As quantum dots,which provides new conditions and requirements for the realization of indistinguishable single photon entanglement source.Strain free Ga As quantum dots may provide a practical platform for the generation of entangled photons in future quantum devices.It provides the experimental basis and optimization scheme for the quantum light source which is urgently needed in quantum communication and quantum computing technology.It also provides the experimental data and theoretical basis for the quantum light source which is needed in all solid-state quantum relay,computing and measurement technology system,and promotes the development of basic research and application of quantum communication,quantum computing and quantum optics.