In-situ Laser-induced Nucleation Of Quantum Dots By Molecular Beam Eqitaxy

The three-dimensional confinement of carriers in semiconductor quantum dots(QDs)reveals unique optoelectronic properties,which push a broad application in optoelectronics and microelectronics.With the requirement by development of science,ordered semiconductor QDs need further improvement.The conventional technology for fabricating ordered semiconductor QDs is by self-assembled epitaxial growth on a patterned substrate.However,the processing of fabricating patterned substrate requires etching,which induces large number of defects in the semiconductor QDs besides the complex of lithography technology.In order solve such problem,it is very significant to develop a new approaching for defect-free semiconductor QDs by simple fabrication processing to achieve high quality ordered semiconductor QDs.In this thesis,based on the combination of molecular beam epitaxy(MBE)and laser interference patterning,a totally new technology was developed to achieve semiconductor QD nucleation by in-situ laser irradiation on strain InGaAs layer grown on GaAs substrate with photo-induction In segregation.(1)The in-situ nucleation of QDs on a strained InGaAs layer grown on GaAs substrate induced by irradiation of a single laser beam was demonstrated.The mechanism of the influence of laser intensity on the photo-nucleation process was discussed.It was found that laser light could control the density of QDs quickly and in a large range of light intensity.(2)On the strained InGaAs layer on GaAs substrate,as the nucleation of QDs induced in-situ by a single laser beam,the influence of the substrate temperature on the photonucleation and the mechanism were studied.It was found that photo-nucleation of the QDs occurred at a large range of substrate temperature.The temperature was the main factor that determines the size of QDs(3)It was experimentally demonstrated that the irradiation by double-beam in-situ laser interference induced nucleation of ordered QDs on the strained InGaAs layer on the GaAs substrate.The influence of laser intensity and substrate temperature on the ordered nucleation were discussed.A phenomenon of "super interference periodicity" was discovered.The research in this thesis is expected to provide a new technical approaching for orderly,controllable,and defect-free QDs.