Navigation Links
'Racetrack' for fast electrons in semiconductor structures
Date:8/29/2008

In order to realize the electrical units of voltage, resistance and current with highest accuracy quantum effects in nano-circuits are nowadays used. Important prerequisites are extremely pure semiconductor layers where high-mobile electrons move through the crystal without collision with residual impurities. To be prepared for future developments in quantum metrology PTB has set up a new molecular beam epitaxy system optimized for the fabrication of highest purity semiconductor structures. Already the first structures have shown ex-treme high electron mobility with a value five times better compared to the ones from the conventional epitaxy system. With this, PTB extends its leading position in electrical quantum metrology with semiconductor structures.

Semiconductors are the basic material for computer and home electronics. In electrical quantum metrology semiconductor devices are used in two areas. First, electrical resis-tance values are reproduced by the quantum-Hall effect with uncertainties below one part in a billion. Second, high mobile electron devices are used to fabricate single-electron pumps allowing controlled transport of electrons passing the device one by one. These single-electron pumps are a hot topic in metrology, today since they might allow the redefinition of the electrical current as a product of frequency and electron charge. Such definition would connect the current unit Ampere to a spatial and time invariant fundamental constant, the elementary charge.

For both applications semiconductor heterostructures made of GaAs and AlGaAs are em-ployed. In those crystals a few nanometer thin electron layer forms at the interface be-tween both materials which is called two-dimensional electron gas. The mobility of these electrons increases with decreasing impurities collisions and it is therefore a measure for the quality of the semiconductor structure.

The fabrication of pure semiconductors is achieved by molecular-beam epitaxy. In an ultrahigh vacuum chamber the source materials, e.g. gallium and arsenic, are evaporated at a background pressure 15 orders of magnitude lower than atmospheric pressure. The growth is highly controlled allowing deposition of atomic layers of GaAs and AlGaAs one by one.

The purity of the semiconductor crystal is determined by the quality of the vacuum in the molecular beam epitaxy system. PTB's new facility has an extremely powerful pumping system to produce ultra-low pressure in the growth chamber. Moreover, special cooling panels, adsorb residual impurities before they can be incorporated in the semiconductor crystal.

The result of these efforts are two-dimensional electron gases with electron mobilties up to 7.5 million cm2/Vs at low temperatures which is a five times higher compared to sam-ples from the standard epitaxy machine. The new structures thus provide a formula-1 race track for electrons to achieve highest mobilties.

By means of the new epitaxial technology PTB will promote the development of semicon-ductor single-electron pumps. Furthermore, the universality of electrical quantum Hall resistance metrology will be investigated focussing on measurements of the fractional quantum Hall effect.


'/>"/>

Contact: Klaus Pierz
Klaus.Pierz@ptb.de
49-053-159-22412
Physikalisch-Technische Bundesanstalt (PTB)
Source:Eurekalert

Related biology technology :

1. UM physicists show electrons can travel over 100 times faster in graphene than in silicon
2. Collaboration yields the right glasses for observing mystery behavior in electrons
3. Quantum device traps, detects and manipulates the spin of single electrons
4. Scientists demonstrate highly directional semiconductor lasers
5. Detecting smallest contaminations on semiconductors with aid of synchrotron radiation
6. First semiconductor-based PET scanner demonstrates potential to aid in early diagnosis of disease
7. SAFC Hitech Launches Metalorganic Bulk Vapor Distribution System for Compound Semiconductor Manufacturing
8. SAFC Hitech Introduces Large Scale Bubbler for Compound Semiconductor Production
9. Engineers demonstrate first room-temperature semiconductor source of coherent Terahertz radiation
10. New polymer could improve semiconductor manufacturing, packaging
11. Hybrid semiconductors show zero thermal expansion; Could lead to hardier electronics
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:7/20/2017)... , ... July 20, 2017 , ... VIC Technology ... joining the company’s board of directors. This addition continues to strengthen and diversify ... Calvin Goforth, CEO and Chairman. “He is a highly accomplished business executive with a ...
(Date:7/20/2017)... DENVER and PLYMOUTH, Minn., July 20, 2017 ... LLC , a personalized genetic evaluations company, today ... under their partnership investigating a genetic mutation implicated ... to extend the partnership for a second case ... Last year, the KCNQ2 Cure Alliance and Pairnomix ...
(Date:7/20/2017)... (PRWEB) , ... July 20, 2017 , ... ... solution to make clinical trial sites and study participants truly unified. TrialKit, a ... compliant (FDA 21 CFR Part 11) research studies entirely on mobile devices. With ...
(Date:7/18/2017)... Vineland, New Jersey (PRWEB) , ... July 18, 2017 , ... ... manufacturer that aligns with your needs and has the capabilities to properly execute your ... web site customglassparts.com is a sourcing portal designed to showcase the ...
Breaking Biology Technology:
(Date:6/14/2017)... -- IBM (NYSE: IBM ) is introducing several innovative partner ... developing collaboration between startups and global businesses, taking place in ... event, nine startups will showcase the solutions they have built ... France is one of ... 30 percent increase in the number of startups created between ...
(Date:5/16/2017)... , May 16, 2017  Veratad Technologies, LLC ( ... online age and identity verification solutions, announced today they ... Conference 2017, May 15 thru May 17, 2017, in ... and International Trade Center. Identity impacts ... and in today,s quickly evolving digital world, defining identity ...
(Date:5/6/2017)... -- RAM Group , Singaporean based technology ... biometric authentication based on a novel  quantum-state ... perform biometric authentication. These new sensors are based on a ... Group and its partners. This sensor will have widespread ... security. Ram Group is a next generation sensor ...
Breaking Biology News(10 mins):