Epitaxial growth

When a thin silicon layer is grown epitaxially on a relaxed SiGe layer with a larger lattice constant, what strain develops in the silicon?

  1. ACompressive strain
  2. BNo strain
  3. CTensile strain
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Answer: C. Tensile strain

Silicon's lattice constant is smaller than SiGe's, so when grown on SiGe, the spacing of silicon atoms is stretched to match the SiGe, producing tensile strain. Tensile-strained silicon has higher electron mobility and has been used to improve nMOS performance.

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More Epitaxial growth questions

  1. Which are the main quality items controlled for epitaxial wafers?
  2. In SiC epitaxial growth, what is the main reason for using substrates tilted a few degrees from the crystal axis (with an off-angle)?
  3. Which is an advantage of performing silicon epitaxial growth at reduced pressure?
  4. Which method measures the thickness of a lightly doped epitaxial layer on a heavily doped substrate using infrared interference?
  5. What is the main challenge in growing GaN on Si substrates?