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span style font-family Times New Roman serif font-size 12pt The optoelectronic integration technique based on Si has become one of the most important research frontiers in the development of modern information technology in order to realize ultra-high speed and ultra-low loss optical interconnection and the most crucial problem is how to successfully fabricate light emitting materials and laser devices based on Si Among various kinds of lasers quantum dot QD lasers have such advantages as low threshold current density insensitive to defects high characteristic temperature high optical gain and so on Therefore there will be important significance and broad application prospects to develop QD epitaxial materials and laser devices on Si Aiming at fabricating QD lasers on Si in this dissertation we concentrate on the epitaxy of GaAs films and self-assembly InAs QDs on Si and Ge by MBE And the physical properties of these materials are also studied In addition the structural design and the fabrication of QD lasers on Si have also been studied preliminarily The related work and results are summarized as follows span span style font-family Times New Roman serif font-size 12pt span span 1 The epitaxy of GaAs films on Si by MBE was studied using two-step growth method in order to explore the optimized conditions for mirror-like GaAs Si surface with less defects And the basic mechanism of the initial growth was also studied span span style font-family Times New Roman serif font-size 12pt span span 1 It was found that span GaAs islands were formed at the initial growth stage and then span g span radually coalesced to a planar GaAs Si surface span which was corresponding to the image transformation from spotty pattern to streaky pattern observed by RHEED And the critical thickness for transformation was about 200 nm span span style font-family Times New Roman serif font-size 12pt span span 2 The surface morphology of GaAs films on Si with nucleation layer grown at different temperatures were investigated It was found that the most optimized temperature for the growth of nucleation layer was span class style151 span 300 span span span span class style151 span style font-family font-size 12pt span span span class style151 span style font-family Times New Roman serif font-size 12pt When the temperature was lower initial GaAs islands would be overlapped resulting in larger surface undulation and when it was higher the density of initial GaAs islands would be lower resulting in surface defects due to the span span font size 3 span font face Calibri font span span style font-family Times New Roman serif font-size 12pt incomplete coalescence process span font span style font-family Times New Roman serif font-size 12pt span span 3 The surface morphology of GaAs films on Si with nucleation layer grown at different span span span style font-family font-size 12pt span span span span span style font-family Times New Roman serif font-size 12pt span span span span span span style font-family font-size 12pt span span span span span span style font-family Times New Roman serif font-size 12pt ratio span span span span style font-family Times New Roman serif font-size 12pt s were investigated It was found that the most optimized span span style font-family font-size 12pt span span style font-family Times New Roman serif font-size 12pt span span style font-family font-size 12pt span span style font-family Times New Roman serif font-size 12pt ratio for the growth of nucleation layer was 14 When the value was lower bigger initial GaAs islands would be formed resulting in larger surface undulation and when it was higher the surface defects would be more due to the low-density initial GaAs islands span span style font-family Times New Roman serif font-size 12pt span span 4 The initial GaAs islands coalesced with the increase of thickness But if the nucleation layer was too thick the surface RMS value would be higher because the migration of Ga atoms was inactive at low temperature which would result in large surface undulation span span span span style font-family Times New Roman serif font-size 12pt span span 5 Growing the nucleation layer by MEE method was helpful to reduce the value of surface undulation And annealing the nucleation layer would rearrange or even destroy the initial GaAs islands span span style font-family Times New Roman serif font-size 12pt span span 2 A new method named as four-step growth was proposed by successively inserting a low temperature LT and an intermediate temperature IT GaAs buffer layer span span span style font-family Times New Roman serif font size 3 font span span span span span style font-family Times New Roman serif font-size 12pt A 1 m thick GaAs epilayer on Si with span span span span style font-family Times New Roman serif font-size 12pt mirror-like surface less defects and reduced roughness was obtained while the full width at half maximum FWHM value of the GaAs 004 peak from double crystal x-ray diffraction -scan was just 210 6 arcsec span span style font-family Times New Roman serif font-size 12pt span span 1 The surface morphology of GaAs films on Si with inserting the LT buffer layer or not were investigated It was found that the LT buffer could effectively reduce surface defects and roughness due to its protection for the initial GaAs islands span span style font-family Times New Roman serif font-size 12pt span span 2 The surface morphology of GaAs films on Si with inserting the IT buffer layer or not were investigated It was found that the IT buffer layer played an important role in promoting the growth transformation from 3D to 2D mode further span span style font-family Times New Roman serif font-size 12pt 3 Based on the high-quality GaAs epilayer on Si grown by four-step method the dislocation blocking layer was grown Through the reasonable design of growth parameters the threading dislocations originated from the GaAs Si interface were effectively blocked span span style font-family Times New Roman serif font-size 12pt 4 Based on the optimized GaAs buffer and dislocation blocking layer the structure of a QD laser on Si was desgined and grown by MBE in one run The density and wavelength at room temperature of these QDs were 2 1 span font size 3 span style font-family Times New Roman serif span span style font-family Times New Roman serif font-size 12pt 10 sup 10 sup cm sup -2 sup span span style font-family Times New Roman serif and span span style font-family Times New Roman serif font-size 12pt 1 22 span span style font-family Times New Roman serif span span style font-family Times New Roman serif font-size 12pt m respectively In addition the fabrication of QD laser devices on Si was studied preliminarily The EL light emitting wavelength at about 1 26 m was realized span font span style font-family Times New Roman serif font-size 12pt 5 In order to grow high-quality GaAs buffer and QD laser materials on Ge Si vitual substrates the growth of GaAs epilayer on Ge was studied Through optimizing the growth temperature and span span style font-family font-size 12pt span span style font-family Times New Roman serif font-size 12pt span span style font-family font-size 12pt span span style font-size 12pt font face Calibri font span span style font-family Times New Roman serif font-size 12pt ratio a 1 m thick GaAs epilayer on Ge with mirror-like surface less defects and reduced roughness was obtained On this basis self-assembly InAs QDs with a density of 4 5 span span class style151 span style font-family Times New Roman serif font-size 12pt 10 sup 10 sup cm sup -2 sup span span span class style151 span style font-family Times New Roman serif font-size 12pt and PL light wavelength of span span span class style151 span style font-family Times New Roman serif font-size 12pt 1 30 span span span class style151 span style font-family font-size 12pt span span span style font-family Times New Roman serif font-size 12pt m were also grown on Ge successfully span

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