Joanna Millunchick

The Materials Science of Metamorphic Buffer Layers for High Performance Device Applications

I investigate the growth, stress, and morphological evolution of metamorphic buffer layers, grown on GaAs substrates by molecular beam epitaxy (MBE). The research focuses on GaAsSb and AlGaAsSb buffer layer designs. These layers seem to have higher nucleation rate of pure-edge dislocations, which are more efficient to relief the strain between the mismatched layers. Since pure-edge dislocations are sessile, the propagation of dislocations to the active region could be significantly reduced. I monitor the stress evolution in situ by multi-beam optical stress sensor (MOSS). This real time data is combined with detailed analysis of data obtained from x-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM).
Highlights (Click an image for more information)
  • HRTEM GaAsSb image

    Fourier-filtered (110) cross-sectional HRTEM image of 608 Å thick GaAs0.5Sb0.5 film. Apparent in the image are one 60º dislocation and a Lomer misfit dislocations.