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Molecular beam epitaxy, abbreviated MBE, is the deposition of one or more pure materials onto a single crystal wafer, one layer of atoms at a time, under ultra-high vacuum, forming a perfect crystal. In solid-source MBE, ultra-pure elements such as gallium and arsenic are heated in separate furnaces until they each slowly begin to evaporate. The evaporated elements (although strictly speaking the arsenic in this case is actually in a molecular form) condense on the wafer, where they react with each other, forming, in this case, gallium arsenide. The term "beam" simply means that evaporated atoms do not meet each other or any other gases until they reach the wafer. Epitaxy is the growth of crystals of one material on the crystal face of another material, such that the crystalline substrates of both materials have the same structural orientation. ...
General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white Atomic mass 69. ...
General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ...
This article is about the chemical compound. ...
A computer controls shutters in front of each furnace, allowing precise control of the thickness of each layer, down to a single layer of atoms. Intricate structures of layers of different materials may be fabricated this way. Such control has allowed the development of structures where the electrons can be confined in space, giving quantum wells or even quantum dots. Such layers are now a critical part of many modern semiconductor devices, including semiconductor lasers and light emitting diodes. A quantum well is a potential well that confines particles in one dimension, forcing them to occupy a planar region. ...
A quantum dot is a potential well that confines electrons in three dimensions to a region of the order of the electrons de Broglie wavelength in size, a few nanometers in a semiconductor. ...
A laser diode is a laser where the active medium is a semiconductor p-n junction similar to that found in a light-emitting diode. ...
Various light-emitting diodes (5 mm reds, 3 mm greens and yellows) A light-emitting diode (LED) is a semiconductor device that emits incoherent monochromatic light when electrically biased in the forward direction. ...
During operation, RHEED (Reflection High Energy Electron Diffraction) is often used for monitoring the growth of the crystal layers. RHEED stands for Reflection High Energy Electron diffraction. ...
The ultra-high vacuum environment within the growth chamber is maintained by a system of cryopumps, and cryopanels, chilled using liquid nitrogen to a temperature of 77 kelvins (-196 degrees Celsius). The wafers on which the crystals are grown are mounted on a rotating platter which can be heated to several hundred degrees Celsius during operation. Vacuum pump that condenses the gas or vapour on a cold surface. ...
The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ...
The degree Celsius (°C or ℃ (Unicode 0x2103)) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. ...
Molecular beam epitaxy is also used for the deposition of some types of organic semiconductors. In this case, molecules, rather than atoms, are evaporated and deposited onto the wafer. Other variations include gas-source MBE, which resembles chemical vapor deposition but in vacuum. This article needs to be cleaned up to conform to a higher standard of quality. ...
DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ...
The term "molecular" beam is used for historical reasons even when atoms, rather than molecules, are being evaporated.
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