Molecular Beam Epitaxy Julia Vice 17 November 2004

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Molecular Beam Epitaxy Julia Vice17 November
2004
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What is MBE?andWhy is it Important?

• Ultra-High-Vacuum based technique for producing
  epitaxial structures with monolayer control
• Epitaxial growing crystalline layers on a
  cyrstalline substrate
• Used in the construction of quantum wells, dots
  and wires for use in lasers
• Heterojunction Bipolar Transistors (HBTs) used in
  satellite communications
• Electronic and Optoelectronic devices (light
  emitting diodes for laser printers, cd and dvd
  players)

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The MBE SystemHow it Works

• Vacuum System
• Liquid N2 cryopanels
• Effusion Cells
• Substrate Manipulator

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The Growth Process

• 3 Phases
• Crystalline phase of the growing
  substrate
• Disordered gas phase of the molecular
• beams
• Near-surface transition layer between
  the
• crystalline and gas phases

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Surface Processes

• Desorption re-evaporate
• Form 2-dimensional clusters with other atoms
• Adsorption incorporate with the substrate
• Migrate along a step to be incorporated at a kink
• Key Controllable Factors the surface and
  temperature of the subtrate and the molecular
  flow

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Surface Processes
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Advantages and Disadvantages of MBE

• Positive Aspects
• High material purity
• Good control of layer thickness and composition
• Easily monitored with RHEED (Reflective High
  Energy Electron Diffraction)

• Negative Aspects
• Low growth rate and substrate-size capability
• Low yields

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Sources

• Anselm, Alex. An Introduction to MBE Growth.
  http//www.ece.utexas.edu/projects/ece/mrc/groups/
  street_mbe/mbechapter.html
• Biasiol, G. and L. Sorba. Molecular Beam
  Epitaxy Principles and Applications. 2001.
  http//tasc.infm.it/tasc/semic/hmmbe/school.pdf
• Physics of Thin Films. 2004.
  http//www.uccs.edu/tchriste/courses/PHYS549/549l
  ectures/mbe.html
• Veeco Learning Center. Molecular Beam
• Epitaxy. 2004. http//www.veeco.com/learnin
  g/learning_
• molecularbeam.asp