Smallest logic circuit fabricated with single-electron transistors

Nov 21, 2012 by Lisa Zyga feature
Researchers have fabricated a half-adder logic circuit with just three SETs and two FETs, compared with 20 FETs in a traditional CMOS half-adder. The new half-adder’s small size and ultra-low power consumption make it promising for next-generation terabit-level nanoelectronics. Image credit: S. J. Kim, et al. ©2012 American Institute of Physics

(Phys.org)—In order to meet the growing demand for small-scale, low-power computing, researchers have been aggressively downscaling silicon-based computing components. These components include transistors and logic circuits, both of which are used to process data in electronic devices by controlling voltage. However, the smallest type of logic circuit, called a half-adder, has not yet been fabricated on as small a scale as it could be.

In a new study, a team of researchers from South Korea, Japan, and the UK has fabricated a half-adder logic circuit using just five transistors Their paper, titled "One electron-based smallest flexible logic cell," is published in a recent issue of Applied Physics Letters.

"We made the first successful implementation of a one-electron-based half-adder (HA) that is the smallest arithmetic block for the single-electron transistor (SET) multi-valued (MV) logic family," Jung-Bum Choi, Professor of Physics and the Director of the Physics Department & Research Institute for Nano Science and Technology at Chungbuk National University in Cheongju, South Korea, told Phys.org. "All logic circuits are just combinations of numerous HAs. The one-electron HA operates at nA-levels with low-power consumption. Moreover, the HA has two additional functionalities: multi-valued and flexible. Therefore, the one-electron HA cell will provide a basis for ultra-high density and low-power ultra-large-scale integration, which is one of the most critical problems facing future small mobile IT systems."

As the smallest arithmetic block of , a half-adder adds two single-digit numbers and generates two outputs: sum and carry, where the carry is added to the next digit in multi-digit addition. In a traditional CMOS half-adder, at least 20 field-effect (FETs) are needed for a half-adder. Here, the scientists fabricated a half-adder with just three SETs and two FETs.

In addition, the scientists showed that the half-adder mode could be switched to a subtraction mode simply by changing the control gate on an SET. In subtraction mode, the sum and carry functions became difference and borrow functions.

"The one-electron HA adapts a new SET structure with two symmetrical side-gates, which enables us to use only three SETs and two FETs components," Choi said. "This cell structure has a considerable advantage in the number of components compared with the traditional CMOS counterpart, where at least 20 FETs are needed for an HA. Moreover, the CMOS is binary, that is, operates with 0 or 1. In contrast, the one-electron HA is multi-valued and flexible, resulting in effective integration density. However, the one-electron HA has previously been delayed in its implementation because the three SETs should have identical phases in their Coulomb oscillations, which has been a very difficult problem occurring mainly due to a highly complicated nanofabrication process."

Due to its small size, ultra-low power consumption, and fast operation, the half-adder logic cell could prove useful for next-generation terabit-level nanoelectronics. Choi hopes it will have applications in the memory and CPU in both mobile systems and PCs. Although it currently operates at a low temperature of 10K, the researchers are currently working on ways to implement the logic circuit at room temperature.

"The flexible multi-valued one-electron HA cell, even though it operates at a low temperature of 10K, provides the smallest block for the SET MV logic family," Choi said. "Most recently, we successfully fabricated the room-temperature multiple switching Si-SET. Using these SETs as basic elements, we expect the possible implementation of the single-electron flexible MV half-adder operating at room-temperature, which is now being undertaken."

Explore further: Infineon offers application optimized bipolar power modules introducing cost-effective solder bond modules

More information: S. J. Kim, et al. "One electron-based smallest flexible logic cell." Applied Physics Letters 101, 183101 (2012). DOI: 10.1063/1.4761935

Journal reference: Applied Physics Letters search and more info website

4 /5 (19 votes)

Related Stories

Molecular algebra in mammalian cells

Jun 04, 2012

(Phys.org) -- Mammalian cells can now do what an electronic calculator can: perform logical calculations. Swiss researchers have equipped cells with a complex genetic network that can do more than just one ...

Recommended for you

A green data center with an autonomous power supply

45 minutes ago

A new data center in the United States is generating electricity for its servers entirely from renewable sources, converting biogas from a sewage treatment plant into electricity and water. Siemens implemented ...

After a data breach, it's consumers left holding the bag

1 hour ago

Shoppers have launched into the holiday buying season and retailers are looking forward to year-end sales that make up almost 20% of their annual receipts. But as you check out at a store or click "purchase" on your online shopping cart ...

Can we create an energy efficient Internet?

1 hour ago

With the number of Internet connected devices rapidly increasing, researchers from Melbourne are starting a new research program to reduce energy consumption of such devices.

Brain inspired data engineering

2 hours ago

What if next-generation ICT systems could be based on the brain's structure and its cognitive and adaptive processes? A groundbreaking paradigm of brain-inspired intelligent ICT architectures is being born.

E-Voting: Risky technology or great improvement?

2 hours ago

On this forthcoming weekend the Australian state election takes place, and in Victoria State they will be using a new e-voting system to improve secrecy, reliability and user-friendliness. But how secure are such systems? ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

hb_
not rated yet Nov 22, 2012
10 K operation is not bad for a SET, that is, if it has resonable performance in other characteristics. I would also commend the writer for making sure that there is a scale bar in the SEM image. Well done!
Lurker2358
1 / 5 (1) Nov 22, 2012
One wonders if the cost of cooling a system to these temperatures is even worth the returns compared to higher operating temperatures or less efficient circuitry?

This is ridiculously, stupidly impractical, even for military, university, or corporate super-computers.
RealScience
4 / 5 (1) Nov 25, 2012
@Lurker: Yes, 10K would be impractical, but that is just a stepping stone. Please re-read their concluding remark:
"Most recently, we successfully fabricated the room-temperature multiple switching Si-SET. Using these SETs as basic elements, we expect the possible implementation of the single-electron flexible MV half-adder operating at room-temperature, which is now being undertaken."

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.