| Summary: | 碩士 === 國立中山大學 === 光電工程研究所 === 91 === Abtract
In this thesis, our purpose is to improve the refractive index models for direct-gap semiconductors. For refractive index spectrum of direct-gap compound semiconductors, most experimental data is available only bellow the bandgap absorption edge. For used in the optimum design of eltro-optic devices, such as waveguide, electro-absorption modulator and Mach-Zehnder interferometer. We have to utilize a little experimental data to extend refractive index spectrum to near and just above the band-gap edge.
We have known that square of refractive index ( ) is dielectric constant ( ), so we decompose the dielectric constant ( ) into the part of band-to-band absorption and another part of single-oscillator high energy absorption.
For the part of band-to-band absorption, we added broadening parameter ( ) and used Kramers-Kronig relation to transform the absorption coefficient into dielectric constant. For another part of single-oscillator high energy background absorption, we first cut the absorption part form experimental data and then use Sellmeier’s equation to fit the residue data. Finally, recombine all equations and extend refractive index spectrum to near and just above the band-gap edge.
We successfully built whole model and confirm our model with GaAs. The calculation result on GaAs shows an excellent agreement with the reported experimental data. Furthermore, We apply our model to direct-gap binary、ternary and quaternary compounded materials and extend our model to near and just above the band-gap edge very well.
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