Epitaxial growth

What is the main challenge in growing GaN on Si substrates?

  1. AThe substrate is very expensive
  2. BLarge differences in lattice constant and thermal expansion tend to cause dislocations, cracks and wafer bow
  3. CGaN does not grow at all
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Answer: B. Large differences in lattice constant and thermal expansion tend to cause dislocations, cracks and wafer bow

The large lattice mismatch between GaN and silicon generates many dislocations, and the large difference in thermal expansion makes cracks and wafer bow likely when cooling after growth. Engineering buffer layers such as AlN and AlGaN has made GaN growth on large-diameter Si substrates practical.

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More Epitaxial growth questions

  1. What is it called when doping gas is flowed during epitaxial growth to add dopants at the same time as growth?
  2. What is the periodic structure called in which layers of different materials, each only a few nm thick, are stacked alternately?
  3. Which technology is used to form the base layer of a SiGe HBT?
  4. Compared with thermal diffusion, what is an advantage of adding dopants during epitaxial growth?
  5. In advanced CMOS processes, why is it necessary to lower the temperature of silicon and SiGe epitaxial growth?