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Related Experiment Videos

Screw dislocations in GaN grown by different methods.

Z Liliental-Weber1, D Zakharov, J Jasinski

  • 1Lawrence Berkeley National Laboratory, m/s 62R0203-8255, Berkeley, CA 94720, USA. z_liliental-weber@lbl.gov

Microscopy and Microanalysis : the Official Journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada
|August 13, 2004
PubMed
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Screw dislocations in hydride-vapor-phase-epitaxy (HVPE) layers contain voids, unlike those in molecular-beam-epitaxy (MBE) overlayers. Dislocation cores in MBE are stoichiometric, while HVPE cores may have higher Ga concentrations, potentially with oxygen at void tips.

Area of Science:

  • Materials Science
  • Solid-State Physics
  • Nanotechnology

Background:

  • Screw dislocations are critical defects influencing material properties.
  • Understanding dislocation core structures is essential for semiconductor material development.
  • Hydride-vapor-phase-epitaxy (HVPE) and molecular-beam-epitaxy (MBE) are key growth techniques for semiconductor layers.

Purpose of the Study:

  • To investigate and compare the characteristics of screw dislocations in HVPE and MBE grown semiconductor materials.
  • To determine the atomic structure and composition within the cores of screw dislocations.
  • To identify the presence and nature of any defects, such as voids, associated with these dislocations.

Main Methods:

  • Transmission electron microscopy (TEM) was employed in both plan-view and cross-sectional configurations.

Related Experiment Videos

  • High-resolution TEM imaging was combined with image simulations using advanced models.
  • Direct reconstruction of scattered electron wave phase and amplitude from focal series was utilized.

    • Main Results:

    • Screw dislocations in HVPE layers exhibited decoration by small voids along the screw axis.
    • No voids were observed along screw dislocations in MBE overlayers, irrespective of growth conditions (Ga-lean or Ga-rich).
    • Dislocation core analysis revealed filled cores in both material types; MBE cores were stoichiometric, while HVPE cores suggested higher Ga concentration and potential oxygen presence at void tips.

    Conclusions:

    • The presence or absence of voids associated with screw dislocations differs significantly between HVPE and MBE growth methods.
    • Dislocation core structures are filled, with distinct compositional differences observed between HVPE and MBE materials.
    • The findings suggest that void formation in HVPE may be linked to specific elemental incorporation, possibly involving oxygen.