Epitaxial wafer

An epitaxial wafer[1] (also called epi wafer,[2] epi-wafer,[3] or epiwafer[4]) is a wafer of semiconducting material made by epitaxial growth (epitaxy) for use in electronics.

Silicon epi wafers were first developed around 1966, and achieved commercial acceptance by the early 1980s.[5] Two methods of growing the epitaxial layer on existing silicon or other wafers are currently used: metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These wafers are sometimes newer types of semiconductors such as gallium nitride (GaN), or some combination of the elements gallium, indium, aluminum, nitrogen, phosphorus or arsenic.

Microelectronic devices such as light-emitting diodes (LEDs) often use epi wafers.

Photovoltaics

Solar cells, or photovoltaic cells (PV) for producing electric power from sunlight can be grown as thick epi wafers on a monocrystalline silicon "seed" wafer by atmospheric-pressure CVD in a high-throughput inline process, and then detached as a self-supporting wafers of some standard thickness (e.g., 250 µm) that can be manipulated by hand, and directly substituted for wafer cells cut from monocrystalline silicon ingots. Solar cells made with this technique can have efficiencies approaching those of wafer-cut cells, but at appreciably lower cost.[6] In September 2015, the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) announced the achievement of an efficiency above 20% for such cells. The work on optimizing the production chain was done in collaboration with NexWafe GmbH, a company spun off from Fraunhofer ISE to commercialize production.[7]

References

Notes

  1. ↑ Swinger, pp. 20, 21, 40, 47.
  2. ↑ Claeys, Cor L. (2006). High Purity Silicon 9, Issue 4. The Electrochemical Society. p. 162. ISBN 9781566775045.
  3. ↑ Hua, Y. N. Identification of Silicon Crystalline Defects on Epi-Wafer in Wafer Fabrication. Chartered Semiconductor Mfg. Ltd., 2001.
  4. ↑ Szweda, R. Diode Laser Materials & Devices – A Worldwide Market & Technology Overview to 2005. Elsevier, 2001. p. x.
  5. ↑ Swinger, pp. 20–22.
  6. ↑ Rachow, Thomas; Heinz, Friedemann; Steinhauser, Bernd; Janz, Stefan; Reber, Stefan (2014). "Epitaxial n- and p-type Emitters for High Efficiency Solar Cell Concepts". Journal of Energy and Power Engineering 8 (David Publishing). pp. 1371–1377. Retrieved October 15, 2015.
  7. ↑ Janz, Stefan; Reber, Stefan (14 September 2015). "20% Efficient Solar Cell on EpiWafer". Fraunhofer ISE. Retrieved October 15, 2015.


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