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 January 30, 2015 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 January 30, 2015).

Share This


More From ScienceDaily



More Matter & Energy News

Friday, January 30, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nanoscale Sensor Could Help Wine Producers and Clinical Scientists

Nanoscale Sensor Could Help Wine Producers and Clinical Scientists

Reuters - Innovations Video Online (Jan. 30, 2015) — A nanosensor that mimics the oral effects and sensations of drinking wine has been developed by Danish and Portuguese researchers. Jim Drury saw it in operation. Video provided by Reuters
Powered by NewsLook.com
Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

RightThisMinute (Jan. 29, 2015) — If your car has an "Insane Mode" then you know it&apos;s fast. Well, these unsuspecting passengers were in for one insane ride when they hit the button. Tesla cars are awesome. Video provided by RightThisMinute
Powered by NewsLook.com
Now Bill Gates Is 'Concerned' About Artificial Intelligence

Now Bill Gates Is 'Concerned' About Artificial Intelligence

Newsy (Jan. 29, 2015) — Bill Gates joins the list of tech moguls scared of super-intelligent machines. He says more people should be concerned, but why? Video provided by Newsy
Powered by NewsLook.com
Senate Passes Bill for Keystone XL Pipeline

Senate Passes Bill for Keystone XL Pipeline

AP (Jan. 29, 2015) — The Republican-controlled Senate has passed a bipartisan bill approving construction of the Keystone XL oil pipeline. (Jan. 29) Video provided by AP
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