Faster and more efficient computer chips thanks to germanium – Phys.org

Click here to sign in with or
Forget Password?
Learn more
share this!
48
8
Share
Email
November 8, 2022
by Vienna University of Technology
TU Wien (Vienna) has succeeded in making a new type of material usable for chip technology. This enables faster, more efficient computers and new types of quantum devices.

Current chip technology is largely based on silicon. Only in very special components a small amount of germanium is added. But there are good reasons to use higher germanium contents in the future: The compound semiconductor silicon-germanium has decisive advantages over today’s silicon technology in terms of energy efficiency and achievable clock frequencies.
The main problem here is to establish contacts between metal and semiconductor on a nanoscale in a reliable way. This is much more difficult with a high proportion of germanium than with silicon. The team at TU Wien, however, together with research teams from Linz and Thun (Switzerland), has now shown that this problem can be solved—with contacts made of crystalline aluminum of extremely high quality and a sophisticated silicon germanium layer system. This enables different interesting contact properties—especially for optoelectronic and quantum components.
The problem with oxygen
“Every semiconductor layer is automatically contaminated in conventional processes; this simply cannot be prevented at the atomic level,” says Masiar Sistani from the Institute for Solid State Electronics at TU Wien. First and foremost, it is oxygen atoms that accumulate very quickly on the surface of the materials—an oxide layer is formed.
With silicon, however, this is not a problem: silicon always forms exactly the same kind of oxide. “With germanium, however, things are much more complicated,” explains Masiar Sistani. “In this case, there is a whole range of different oxides that can form. But that means that different nanoelectronic devices can have very different surface compositions and therefore different electronic properties.”
If you now want to connect a metallic contact to these components, you have a problem: Even if you try very hard to produce all these components in exactly the same way, there are still inevitably massive differences—and that makes the material complex to handle for use in the semiconductor industry.
“Reproducibility is a big problem,” says Prof. Walter Weber, the head of the Institute for Solid State Electronics, TU Wien. “If you use germanium-rich silicon germanium, you can’t be sure that the electronic component, after you’ve put contacts on it, will really have the characteristics you need.” As a result, this material is only used to a limited extent in chip production.
That is a pity, because silicon germanium would have decisive advantages: “The charge carrier concentration is higher, especially positive charge carriers, the so-called ‘holes’, can move much more efficiently in this material than in silicon. The material would therefore allow much higher clock frequencies with increased energy efficiency than our current silicon chips,” says Lukas Wind, a doctoral student in Walter Weber’s research group.
The ‘perfect’ interface
Now, however, the research team has been able to show how the problem can be solved: They found a method to create perfect interfaces between aluminum contacts and silicon germanium components on an atomic scale. In a first step, a layer system is produced with a thin silicon layer and the actual material from which the electronic components are to be made—the silicon-germanium.
By heating the structure in a controlled manner, a contact can now be created between the aluminum and the silicon: At around 500 degrees Celsius, distinctive diffusion occurs, the atoms can leave their place and start to migrate. Silicon and germanium atoms move into the aluminum contact relatively quickly, and aluminum fills the vacated space.
“The diffusion dynamics in the layer system used thus create an interface between aluminum and the silicon germanium with an extremely thin silicon layer in between,” explains Masiar Sistani. Through this manufacturing process, oxygen atoms never have the opportunity to get to this atomically sharp and highly pure interface.
“Our experiments show that these contact points can be produced in a reliable and easily reproducible way,” says Walter Weber. “The technological systems you need to do this are already being used in the chip industry today. So, this is not just a laboratory experiment, but a process that could be used relatively quickly in the chip industry.”
The decisive advantage of the presented manufacturing process is that high-quality contacts can be produced regardless of the silicon–germanium composition. “We are convinced that the presented abrupt, robust and reliable metal-semiconductor contacts are highly interesting for a variety of new nanoelectronic, optoelectronic and quantum devices,” says Walter Weber.
The research was published in Small.

More information: Lukas Wind et al, Composition Dependent Electrical Transport in Si_1−xGe_x Nanosheets with Monolithic Single‐Elementary Al Contacts, Small (2022). DOI: 10.1002/smll.202204178

Journal information: Small
Provided by Vienna University of Technology
Explore further
Facebook
Twitter
Email
Feedback to editors
11 hours ago
0
12 hours ago
0
Nov 07, 2022
0
Nov 07, 2022
0
Nov 07, 2022
0
2 hours ago
4 hours ago
4 hours ago
4 hours ago
5 hours ago
5 hours ago
5 hours ago
6 hours ago
6 hours ago
7 hours ago
Oct 11, 2021
Dec 01, 2021
Jan 14, 2020
Mar 01, 2022
Sep 09, 2021
May 15, 2020
7 hours ago
8 hours ago
9 hours ago
Nov 07, 2022
Nov 07, 2022
Nov 07, 2022
Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form. For general feedback, use the public comments section below (please adhere to guidelines).
Please select the most appropriate category to facilitate processing of your request
Thank you for taking time to provide your feedback to the editors.
Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.
Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient’s address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we’ll never share your details to third parties.
More information Privacy policy
Medical research advances and health news
The latest engineering, electronics and technology advances
The most comprehensive sci-tech news coverage on the web
This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use.

source