Segregation in InGaAs/GaAs Stranski-Krastanow layers grown by MOCVD
Résumé
Using quantitative high resolution transmission electron microscopy we studied the chemical morphology of wetting layers in InGaAs/GaAs quantum dot structures which were optimised for applications to optical devices operating around 1.3 ƒÝm. The samples are grown by low-pressure metal-organic chemical vapour deposition on GaAs substrates. Indium concentration profiles of the wetting layers are evaluated with the composition evaluation by the lattice fringe analysis method. The profiles reveal a clear signature of segregation. A fit of the profiles with the Muraki model for segregation (K. Muraki et al., Appl. Phys. Lett. 61 (1992), 557) reveals a segregation efficiency of R=0.65¡Ó0.05 at the growth temperature of 550 ¢XC, which is significantly lower than segregation efficiencies observed in samples grown by molecular beam epitaxy at similar temperatures.
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