indroduction , mechanism of epitaxial growth, motivation, application, summary

1. Ashwani Vishwakarma
ROLL No. –290
MSc-II Inorganic Chemistry
CRYSTAL GROWTH
FROMVAPOR PHASE

2. Outline
• Introduction
• Mechanism of epitaxial growth
• Motivation of epitaxial deposition
• Properties of epitaxial layers
• Applications of epitaxial layers
• Summary

3. What is epitaxial .?
• The method of depositing a mono-crystalline film on a mono-crystalline
substrate .The deposited film is denoted as epitaxial layer.
• The term epitaxy comes form the Greek roots,
Epi means ‘‘above” and
Taxis means “deposition in ordered ”
• Epitaxial films may be grown from gaseous or liquid precursors.
• The substrate acts as a seed crystal, the deposited film takes on a lattice
structure and orientation identical to those on the substrate.

4. Ordered, crystalline
growth; NOT epitaxial
Epitaxial growth:
Mechanism of Epitaxial Growth

5. Types of epitaxial films or layer
• Epitaxial films can be classified into two types:
1) Homoepitaxy
2) Heteroepitaxy
Growth of a layer of a different material than the substrate (GaAs on Si)
Growth of a layer of the same material as the substrate(Si on Si)

6. Motivation
• Epitaxial growth is useful for applications that place stringent
demands on a deposited layer
High purity
Low defect density
Controlled doping profiles
High uniformity
Safe, efficient operation
• Can create clean, fresh surface for device fabrication

7. Methods
• Epitaxial silicon is usually grown using vapor-phase epitaxy (VPE), a
modification of chemical vapor deposition.
• Molecular-beam and liquid-phase epitaxy (MBE and LPE) are also
used, mainly for compound semiconductors. Solid-phase epitaxy is
used primarily for crystal-damage healing.

8. Properties of Epitaxial Layer
• Crystallographic structure of film reproduces that of substrate
• Substrate defects reproduced in epitaxial layer
• Electrical parameters of epitaxial layer independent of substrate
Dopant concentration of substrate cannot be reduced
Epitaxial layer with less dopant can be deposited
• Epitaxial layer can be chemically pure than substrate

9. Applications
• Nanotechnology
• Semiconductor fabrication
• High quality crystal growth (silicon-germanium, gallium arsenide
etc.)
• To deposit organic molecule onto crystalline.

10. Summary
• Deposition continues crystal structure
• Creates clean, interfaces and high quality surfaces
• High temperature, clean surface required
• Vapor phase epitaxy a major method of deposition
• Epitaxial layers used in highest quality wafers

11. References
• Solid State Chemistry and its Applications
BY- ANTHONY R.WEST

12. ThankYou