Epitaxial growth

Check the definition of epitaxial growth, homoepitaxy and heteroepitaxy, lattice mismatch, and MOCVD and MBE with multiple-choice questions.

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Epitaxial growth: key points

Epitaxial growth is a technique for growing a single-crystal thin film on a single-crystal substrate with the same crystal orientation as the substrate. Because it can create layers with precisely controlled impurity concentrations, it is used for power devices, bipolar devices and compound semiconductor devices.

Growing the same material as the substrate is homoepitaxy, and growing a different material is heteroepitaxy. In heteroepitaxy, defects caused by differences in lattice constant (lattice mismatch) must be considered.

All Epitaxial growth questions (50)

  1. Which correctly describes epitaxial growth?
  2. Which is an example of heteroepitaxial growth?
  3. What is MOCVD (metal-organic chemical vapor deposition) mainly used for?
  4. What problem tends to occur when there is a large difference in lattice constant (lattice mismatch) between the substrate and the grown film?
  5. Which is a characteristic of MBE (molecular beam epitaxy)?
  6. Which gases are used as sources for silicon epitaxial growth?
  7. Which correctly describes selective epitaxial growth?
  8. What is the phenomenon called in which impurities from the substrate or elsewhere are incorporated into the growing layer through the gas phase during epitaxial growth?
  9. What is an advantage of a wafer with a lightly doped p-type epitaxial layer grown on a p+ substrate (p/p+ epitaxial wafer)?
  10. Which correctly describes the critical thickness in heteroepitaxial growth?
  11. What is the main purpose of heating the wafer in high-temperature hydrogen just before silicon epitaxial growth?
  12. Why are epitaxial layers important in the fabrication of SiC power devices?
  13. In epitaxial growth by CVD, the growth rate depends strongly on temperature in the relatively low-temperature regime. Why?
  14. Which is a typical crystal defect in epitaxial layers in which the stacking sequence of atomic planes is disrupted?
  15. In GaN and similar materials, what is the technique called that reduces dislocations by growing crystal from mask openings and then laterally over the mask?
  16. Which method grows crystal on a substrate by precipitating it from a solution such as a molten metal?
  17. Which is closest to the typical growth temperature for silicon epitaxy using trichlorosilane?
  18. When a thin silicon layer is grown epitaxially on a relaxed SiGe layer with a larger lattice constant, what strain develops in the silicon?
  19. Which are the main quality items controlled for epitaxial wafers?
  20. In SiC epitaxial growth, what is the main reason for using substrates tilted a few degrees from the crystal axis (with an off-angle)?
  21. Which is an advantage of performing silicon epitaxial growth at reduced pressure?
  22. Which method measures the thickness of a lightly doped epitaxial layer on a heavily doped substrate using infrared interference?
  23. What is the main challenge in growing GaN on Si substrates?
  24. What is it called when doping gas is flowed during epitaxial growth to add dopants at the same time as growth?
  25. What is the periodic structure called in which layers of different materials, each only a few nm thick, are stacked alternately?
  26. Which technology is used to form the base layer of a SiGe HBT?
  27. Compared with thermal diffusion, what is an advantage of adding dopants during epitaxial growth?
  28. In advanced CMOS processes, why is it necessary to lower the temperature of silicon and SiGe epitaxial growth?
  29. Which polytype is mainly used for SiC power devices?
  30. In MBE, which technique observes growth in situ by directing an electron beam at the surface at a grazing angle and examining the diffraction pattern?
  31. What is the origin of the word "epitaxy"?
  32. What is the typical thickness range of the epitaxial layer on silicon epi wafers for LSIs and power devices?
  33. In silicon epitaxial growth, what is the main role of the large flow of hydrogen (H2) supplied along with the source gas?
  34. Which method is used to grow thick GaN layers quickly to make free-standing GaN substrates?
  35. Which is closest to the density of threading dislocations, which run up to the film surface, in GaN grown on sapphire?
  36. In bipolar transistors and similar devices, what is the main purpose of a heavily doped layer (buried layer) beneath the epitaxial layer?
  37. Which is closest to the typical growth temperature for SiC epitaxy (CVD)?
  38. Which type of reactor is mainstream for silicon epitaxial growth on 300 mm wafers?
  39. In heteroepitaxy of materials with very different lattice constants, what is the purpose of inserting a "graded buffer layer" whose composition changes gradually?
  40. 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?
  41. In MOCVD growth of GaN, what does the controlled condition "V/III ratio" mean?
  42. 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?
  43. 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?
  44. 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.
  45. 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?
  46. What is the main purpose of epitaxially growing and embedding Si:C (silicon with a small amount of carbon) in the source and drain of nMOS transistors?
  47. Which research-stage technique grows a crystal on a substrate covered with a 2D material such as graphene so that the grown film can be peeled off and the substrate reused?
  48. In epitaxial structures for GaN HEMTs, what is the main purpose of adding carbon or iron to the GaN buffer layer beneath the channel?
  49. When a polar compound semiconductor such as GaAs is grown on a non-polar silicon substrate, what is the boundary called between regions in which the Ga and As positions are inverted?
  50. In SiC epitaxy, what is the phenomenon called in which many atomic surface steps gather into large steps, roughening the surface?

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