Featured Research

from universities, journals, and other organizations

New Theory Provides Better Understanding Of Transistors

Date:
March 5, 1999
Source:
University Of Illinois At Urbana-Champaign
Summary:
The p-n junction diode is the basic element in nearly all semiconductor devices. Trillions of these diodes -- which permit current to flow only in one direction -- are produced daily. More than 10 million p-n junction diodes can be found in a typical personal computer. However, since the invention of the transistor 50 years ago, certain characteristics of the p-n junction have been poorly understood and improperly described in textbooks. Now, a new theory of p-n junction performance promises to resolve past misconceptions, says a University of Illinois researcher.

CHAMPAIGN, Ill. -- The p-n junction diode is the basic element in nearly all semiconductor devices. Trillions of these diodes -- which permit current to flow only in one direction -- are produced daily. More than 10 million p-n junction diodes can be found in a typical personal computer.

Related Articles


However, since the invention of the transistor 50 years ago, certain characteristics of the p-n junction have been poorly understood and improperly described in textbooks. Now, a new theory of p-n junction performance promises to resolve past misconceptions, says a University of Illinois researcher.

"It may sound strange, but the precise physics of what makes these devices work has not been fully understood," said Karl Hess, a U. of I. Swanlund Professor of electrical and computer engineering and a researcher at the university's Beckman Institute for Advanced Science and Technology. "We found deficiencies in every textbook description of p-n junction diodes. For example, the diffusion capacitance -- the conductance property for alternating current -- was predicted incorrectly in all cases."

Hess and Steven Laux, a researcher at the IBM Thomas J. Watson Research Center who spent a yearlong sabbatical at Illinois, combined computer simulations and numerical analyses to come up with a much more complete understanding of p-n junction performance. They developed a mathematical expression that provides excellent agreement between precise computation and analytical approximation.

"This expression permitted us to identify individual contributions to the diffusion capacitance, and to separate these contributions as they arise from the space-charge or quasi-neutral regions," Laux said. "We therefore have introduced a new set of alternating-current boundary conditions and a more precise treatment of the distribution of the mobile charge."

One surprising result of the new theory is that the diffusion capacitance for long diodes is different from what had been assumed. "Instead of growing exponentially, as taught in all textbooks, the diffusion capacitance actually vanishes in many cases," Hess said.

Why had researchers not identified this before, and how could trillions of well-working p-n junctions have been made without this knowledge?

"Some of the mysteries of p-n junction performance were 'explained' in the past by researchers who inserted erroneous terms into their equations," Hess said. "Fortunately for previous analyses, the mistakes were biggest for long diodes, while most diodes are relatively short. Nevertheless, even very short diodes show deviations from the standard understanding at high forward current densities."

In addition to replacing the previously incomplete and incorrect theories in future textbooks, the new theory should be useful to researchers working with certain types of p-n junctions, such as those used in semiconductor laser diodes.

Laux and Hess describe their new theory in the February issue of IEEE Transactions on Electron Devices.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "New Theory Provides Better Understanding Of Transistors." ScienceDaily. ScienceDaily, 5 March 1999. <www.sciencedaily.com/releases/1999/03/990305070639.htm>.
University Of Illinois At Urbana-Champaign. (1999, March 5). New Theory Provides Better Understanding Of Transistors. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/1999/03/990305070639.htm
University Of Illinois At Urbana-Champaign. "New Theory Provides Better Understanding Of Transistors." ScienceDaily. www.sciencedaily.com/releases/1999/03/990305070639.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA's First 3-D Printer In Space Creates Its First Object

NASA's First 3-D Printer In Space Creates Its First Object

Newsy (Nov. 26, 2014) The International Space Station is now using a proof-of-concept 3D printer to test additive printing in a weightless, isolated environment. Video provided by Newsy
Powered by NewsLook.com
Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Who Will Failed Nuclear Talks Hurt Most?

Who Will Failed Nuclear Talks Hurt Most?

Reuters - Business Video Online (Nov. 25, 2014) With no immediate prospect of sanctions relief for Iran, and no solid progress in negotiations with the West over the country's nuclear programme, Ciara Lee asks why talks have still not produced results and what a resolution would mean for both parties. Video provided by Reuters
Powered by NewsLook.com
Flying Enthusiast Converts Real-Life Aircraft Cockpit Into Simulator

Flying Enthusiast Converts Real-Life Aircraft Cockpit Into Simulator

Reuters - Innovations Video Online (Nov. 25, 2014) A virtual flying enthusiast converts parts of a written-off Airbus aircraft into a working flight simulator in his northern Slovenian home. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins