Presentation on theme: "Quantum Well Structures and Fabrications A PRESENTATION OF THE DIFFERENT QUANTUM WELL STRUCTURES AND THEIR FABRICATION PROCESS BY TIM KOSANKE AND BLAKE."— Presentation transcript:
Quantum Well Structures and Fabrications A PRESENTATION OF THE DIFFERENT QUANTUM WELL STRUCTURES AND THEIR FABRICATION PROCESS BY TIM KOSANKE AND BLAKE CARLSON MAY 1, 2013
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.  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.  The size of the quantum wells are generally between 1 and 20 nm.  Example of a GaAs rectangular well 
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. 
More examples of quantum well structures Example of a parabolic quantum well Second example of rectangular quantum well 
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. 
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.  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.  Typical components and layout of the main chamber of MBE system 
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.  A chemical vapor deposition method using plasma 
Practical Uses of Quantum Well Structures Quantum wells can be seen mostly in the making of diode lasers.  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…  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 
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  Bates, Angie. "What Is a Quantum Well?" WiseGeek. Ed. Lauren Fritsky. Conjecture, n.d. Web. 28 Apr. 2013.. Used to describe what a quantum well is, the behavior of a quantum well, and what they are used in.  "Chemical Vapor Deposition." Wikipedia. Wikimedia Foundation, 21 Apr. 2013. Web. 28 Apr. 2013.. Used to describe the CVD process.  Christensen, Thomas M. "Physics of Thin Films." Molecular Beam Epitaxy. University of Colorado, Colorado Springs, 17 Mar. 2010. Web. 29 Apr. 2013.. Used to explain the MBE process.  Frensley, William R. "Quantum Wells." Quantum Wells. University of Texas, Dallas, 21 May 1995. Web. 28 Apr. 2013.. Used as a resource for rectangular and parabolic quantum well structure pictures.
References Cont.  Knightskross. "U.S. Navy Laser Test Takes Down Drone." YouTube. YouTube, 08 Apr. 2013. Web. 28 Apr. 2013.. Used for video of Navy laser destroying surveillance drone.  "Molecular Beam Epitaxy." Wikipedia. Wikimedia Foundation, 21 Apr. 2013. Web. 28 Apr. 2013.. Used to describe the MBE process.  Schubert, E. F. "Quantum Wells (QWs)." Rensselaer Polytechnic Institute, 2003. Web. 28 Apr. 2013.. Used as a resource for a quantum well structure picture.  "Quantum Well." Wikipedia. Wikimedia Foundation, 29 Mar. 2013. Web. 28 Apr. 2013.. 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.