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.

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 July 22, 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 July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
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:
from the past week

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