Epitaxial growth

In the X-ray diffraction rocking curve used to evaluate the crystal quality of an epitaxial layer, what does a narrow peak width (FWHM) indicate?

  1. AThat there is little tilt, mosaicity or defects, so the crystal quality is good
  2. BThat the impurity concentration is high
  3. CThat the film is thick
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Answer: A. That there is little tilt, mosaicity or defects, so the crystal quality is good

A rocking curve measures the intensity of a particular diffraction peak while slightly varying the sample angle. Variation in crystal orientation (mosaicity) and dislocations broaden the peak, so a narrower FWHM indicates better crystal quality. It is widely used to evaluate epi layers such as GaN.

  • A. Correct. It indicates well-aligned crystal with few defects.
  • B. It is not a direct measure of impurity concentration.
  • C. The FWHM is not a direct measure of thickness.
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More Epitaxial growth questions

  1. In MOCVD growth of GaN, what does the controlled condition "V/III ratio" mean?
  2. When a lightly doped epi layer is grown at high temperature on a heavily doped substrate, what is the phenomenon called in which substrate dopants seep into the epi layer by solid-state diffusion, smoothing the concentration change at the interface?
  3. Which technique, developed by Isamu Akasaki, Hiroshi Amano and colleagues to grow high-quality GaN on sapphire, first deposits a thin layer at low temperature and then grows GaN at high temperature?
  4. In a lattice-mismatched system, which growth mode grows layer by layer for the first few atomic layers and switches to island growth as strain accumulates? It is also used to make quantum dots.
  5. When silicon is grown epitaxially on a substrate with patterns such as buried layers, what is the phenomenon called in which the steps appearing on the surface are offset from the underlying pattern or distorted in shape?