MOCVD Growth And Characteration Of InP/InGaAs Core-shell Nanowires

Ⅲ-Ⅴ semiconductor grown on silicon which can be used for photo-electricmaterial has attracted a lot of attention. Traditional layer heterostructure can hardlyavoid the crystal mismatch and thermal mismatch problem and make it difficult toensure the quality. However, the appearance of nanowire has solved these problemsand made possibility for the future photo-electric device. In the nanowires, crystallattice can zoom in and out at the radial direction, which makes it possible to growfree-standing Ⅲ-Ⅴ semiconductor nanowires on large crystal mismatch substratewith high crystal quality. For quantum size effect, nanowires has many propertiessuch as discrete energy levels, quantum conductance, ballistic transport and coulombblockade which cause a unique performance on electrical, optical and magnetic.InP is Ⅲ-Ⅴ compound semiconductor with direct band gap of1.35eV at roomtemperature. It has high electron mobility and presents dynatron effect. InGaAs isdirect band gap material at all components which can switch from0.35eV to1.43eV.It has fine stability, low effective mass, large light absorption coefficient, highelectron mobility and peak velocity. InP/InGaAs core-shell nanowires can formheterostructure contact at radial direction and realize one dimensional energy bandgap construction which builds light emission and detection at nanoscale. It has greatpotential in single quantum dot geometry, PN junction, bipolar junction andnanosuperstructure. For this consideration, it is important to research on its growth and get high quality core-shell nanowires for characterizing. In this thesis, MOCVDis used to grow InP nanowires at different stages on Si(100) substrate in catalyst-freeway. On this base, InP/InGaAs core-shell nanowires are fabricated and characterizedby Scanning microscope, Transmission electron microscope, X-ray diffraction,Photoluminescence and Raman scattering to get their pattern, growth direction,crystal structure and optical properties.The works which have done in this thesis include:1. Catalyst-free InP nanowires were grown on Si(100) substrate by MOCVD andthe process follows vapor-liquid-solid methods.2. The density change during InP catalyst-free growing process has been found andit is proved that new catalyst can be fabricated in growing process. Singlenanowires at different growing stages has been evaluated and combined withthe result of Raman scattering to study the quality change process. Nanowiresgrow along (111) direction and the band gap decrease as diameter gets larger.3. Catalyst-free InP/InGaAs core-shell nanowires were grown on Si(100) byMOCVD. InP core and InGaAs shell was grown at different temperature and itis realized to adjust the component of InGaAs shell.4. The pattern of the InP/InGaAs core-shell nanowires was studied by SEM. ByTEM and EDX, radial heterostructure was confirmed. Transformation of thecatalyst at the top of the nanowires was characterized by EDX and XRD.