Discovery uncovers the role of oxygen impurities within semiconductor properties
Researchers investigating the properties of semiconductors combined with thin oxide sheets discovered a surprising source of conductivity that is derived from oxygen atoms within.
Scott Chambers, a materials scientist from the Department of Energy’s Pacific Northwest National Laboratory presented the findings of the team at the American Physical Society Spring 2022 meeting. The findings of the study are published in the journal Physical Review Materials. This finding will have profound implications for future semiconductor design and manufacturing. According to the amount of electronic impurities introduced during crystal growth, the semiconductors used in modern electronics can be divided into two types: n/p and n/p. Modern electronic devices can use both n- and the p-type of silicon-based materials. There is a lot of interest in developing new types of semiconductors. Chambers and his colleagues were experimenting with germanium in conjunction with a thin crystalline layer of lanthanum-strontium-zirconium-titanium-oxide (LSZTO). Chambers said that he is reporting on a powerful tool to probe the structure and functions of semiconductors. “Hard Xray photoelectron spectrum revealed that the properties of the material system are dominated by atoms in oxygen when germanium is joined with a particular oxide material. This was quite a surprise.
The Harwell Science and Innovation Campus in Oxfordshire was home to the Diamond Light Source. This enabled the researchers to discover a lot more about the electronic properties and functions of the germanium/LSZTO systems than they had previously been able to with the standard methods.
Chambers stated that “when we tried to probe this material using conventional techniques, the much greater conductivity of germanium caused essentially a short circuit.” “As a consequence, we were able to learn a little about the electronic properties and interface of the LSZTO and Ge. This was something we thought might be very useful and interesting for technology.”
Hard X-rays have a new role
The Diamond Light Source’s so-called “hard” radiation could penetrate the material to reveal information at the atomic level.
Chambers stated that the oxygen impurities in germanium were responsible for the interesting effects observed in their results. Chambers stated that oxygen atoms close to the interface give electrons to the LSZTO films, creating holes or the absence electrons in the germanium within a few atomic layer of the interface. These special holes created behavior that completely eclipsed the semiconducting properties both of n-type and p-type germaniums in the various samples we prepared. This was also a surprise.
Interesting semiconducting properties are often found at the interface between the thin-film silicon and the base semiconductor. Chambers says the challenge is to modify the electric field at the interface to alter the fascinating and useful electric fields. This possibility is being explored at PNNL.
Chambers stated that although the research samples are not commercially viable, the scientific discoveries and techniques used will pay off in the long-term. This new scientific knowledge will allow materials scientists and physicists to better understand how to create new semiconductor material systems that have useful properties.
The research was conducted by PNNL researchers Bethany Matthews and Steven Spurgeon. Mark Bowden, Zihua Zihu, Peter Sushko, Mark Spurgeon, Mark Bowden and Zihua Zihu were also involved. The Department of Energy Office of Science supported the study. The Environmental Molecular Sciences Laboratory is a Department of Energy Office of Science user facility at PNNL. It performed some experiments and prepared samples. The PNNL Radiochemical Process Laboratory was used for electron microscopy. Tien-Lin Lee, Judith Gabel and others performed experiments at Diamond Light Source. Additional collaborators were Joe Ngai and Matt Chrysler from the University of Texas at Arlington, who prepared the samples.