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Quantum Well
Structures and
Fabrications
A P R E S E N TAT I O N O F T H E D I F F E R E N T Q U A N T U M W E L L
S T R U C T U R E S A N D T H E I R FA B R I C AT I O N P R O C E S S B Y T I M
KO S A N K E A N D B L A K E C A R L S O N
M AY 1 , 20 13
Key Concepts
• What is a quantum well and what does it do?
• What materials are used to fabricate the quantum well structures and
methods of fabrication?
• What are the practical uses of quantum well structures and how do
they apply to the real world?
What is a quantum well?
• A quantum well is similar to a
potential well, the difference
being that is only contains
discrete energy values. [8]
• Generally, a quantum well is
formed when a thin layer of a
narrow-gap semiconductor
material lies between a thicker
layer of wider-gap material. [1]
• The size of the quantum wells are
generally between 1 and 20 nm.
[1]
Example of a GaAs rectangular well [4]
The Behavior of Quantum Well Structures
• Band gaps act as a barriers between the ground state bands and
conduction bands, preventing electrons from reaching the
conduction band unless they gain more energy.
• Once an electron reaches the conduction band, the excess energy is
released and the electron falls back to its ground state.
• If the gaps are too wide for electrons to jump easily, thin
semiconductors are placed in the gap area.
• This allows for easy manipulation of the electrons and their energy.
• The wells create narrow streams of energy making it more focused.
[1]
More examples of quantum well structures
Example of a parabolic quantum well [4]
Second example of rectangular quantum well
[7]
Commonly used materials and methods of
quantum well fabrication
• Some of the commonly used materials used to create quantum wells
include: Gallium Arsenide between Aluminum Arsenide and Indium
Gallium Nitride between Gallium Nitride.
• There are two methods of fabrication which include: molecular beam
epitaxy and chemical vapor deposition. [8]
Molecular Beam Epitaxy
• Epitaxy means the growth of a film with
a crystallographic relationship between
substrate and the film.
• Creating quantum wells like this is often
expensive but highly accurate.
• The process is often carried out in a
vacuum and uses multiple alloys to grow
the alloy films. [3]
• Elements are heated until they are
gaseous and then condense onto the
wafer.
• The term beam refers to the evaporated
atoms that do not interact with each
other until they reach the wafer. [6]
Typical components and layout of the
main chamber of MBE system [6]
Chemical Vapor Deposition
• Similar to BME, but instead is a
chemical process where the
wafer is exposed to volatile
precursors, which then react and
decompose on the substrate to
create the film.
• A precursor is a chemical
compound that takes part in the
chemical reactions producing
another chemical compound. [2]
A chemical vapor deposition method using
plasma [2]
Practical Uses of Quantum Well Structures
• Quantum wells can be seen mostly
in the making of diode lasers. [1]
• These lasers include red lasers for
DVDs and handheld laser pointers,
infrared lasers for fiber optic
transmitters, and blue lasers for
Blu-ray players, etc… [7]
• The Navy has recently
demonstrated that a laser can be
used to destroy surveillance
drones.
Video of Navy using a laser to take down a
surveillance drone [5]
Summary and Conclusion
• Quantum wells are potential wells with discrete energy values.
• Quantum wells are formed using one of two methods: molecular
beam epitaxy or chemical vapor deposition.
• Quantum wells are seen mostly in the fabrication of laser diodes.
• Quantum wells have lead to some very useful products in our society,
i.e. Blu-ray lasers, DVD lasers, free electron lasers (medical purposes,
military uses).
References
• [1] Bates, Angie. "What Is a Quantum Well?" WiseGeek. Ed. Lauren Fritsky. Conjecture,
n.d. Web. 28 Apr. 2013. <http://www.wisegeek.com/what-is-a-quantum-well.htm>.
• Used to describe what a quantum well is, the behavior of a quantum well, and what they are used in.
• [2] "Chemical Vapor Deposition." Wikipedia. Wikimedia Foundation, 21 Apr. 2013. Web.
28 Apr. 2013. <http://en.wikipedia.org/wiki/Chemical_vapor_deposition>.
• Used to describe the CVD process.
• [3] Christensen, Thomas M. "Physics of Thin Films." Molecular Beam Epitaxy. University
of Colorado, Colorado Springs, 17 Mar. 2010. Web. 29 Apr. 2013.
<http://www.uccs.edu/~tchriste/courses/PHYS549/549lectures/mbe.html>.
• Used to explain the MBE process.
• [4] Frensley, William R. "Quantum Wells." Quantum Wells. University of Texas, Dallas, 21
May 1995. Web. 28 Apr. 2013.
<http://www.utdallas.edu/~frensley/technical/hetphys/node11.html>.
• Used as a resource for rectangular and parabolic quantum well structure pictures.
References Cont.
• [5] Knightskross. "U.S. Navy Laser Test Takes Down Drone." YouTube. YouTube, 08
Apr. 2013. Web. 28 Apr. 2013. <http://www.youtube.com/watch?v=l5qKSKsfUPM>.
• Used for video of Navy laser destroying surveillance drone.
• [6] "Molecular Beam Epitaxy." Wikipedia. Wikimedia Foundation, 21 Apr. 2013. Web.
28 Apr. 2013. <http://en.wikipedia.org/wiki/Molecular_beam_epitaxy>.
• Used to describe the MBE process.
• [7] Schubert, E. F. "Quantum Wells (QWs)." Rensselaer Polytechnic Institute, 2003.
Web. 28 Apr. 2013. <http://www.ecse.rpi.edu/~schubert/Course-ECSE6290%20SDM-2/1%20QWs%20MQWs%20and%20SLs.pdf>.
• Used as a resource for a quantum well structure picture.
• [8] "Quantum Well." Wikipedia. Wikimedia Foundation, 29 Mar. 2013. Web. 28 Apr.
2013. <http://en.wikipedia.org/wiki/Quantum_well>.
• Used to describe some of the uses of quantum wells and what a quantum well is.
List of Five Key Concepts
• Quantum wells are similar to potential wells but with discrete energy
values.
• Quantum wells are placed so electrons can jump from valence band
to conduction band more easily.
• Quantum wells create a more focused, narrow stream of energy.
• Quantum wells are created using either molecular beam epitaxy or
chemical vapor deposition.
• Quantum wells are seen mostly in the fabrication of laser diodes.