Surprising semiconductor properties revealed with innovative new method
Discovery reveals role of oxygen impurities in semiconductor properties


Date:
March 1, 2022
Source:
DOE/Pacific Northwest National Laboratory
Summary:
Semiconductor experiments reveal a surprising new source of
conductivity from oxygen atoms trapped inside the material.



FULL STORY ==========================================================================
A research team probing the properties of a semiconductor combined
with a novel thin oxide film have observed a surprising new source of conductivity from oxygen atoms trapped inside.


========================================================================== Scott Chambers, a materials scientist at the Department of Energy's
Pacific Northwest National Laboratory, reported the team's discovery at
the Spring 2022 meeting of the American Physical Society. The research
finding is described in detail in the journal Physical Review Materials.

The discovery has broad implications for understanding the role of thin
oxide films in future semiconductor design and manufacture. Specifically, semiconductors used in modern electronics come in two basic flavors --
n-type and p-type -- depending on the electronic impurity added during
crystal growth.

Modern electronic devices use both n- and p-type silicon-based
materials. But there is ongoing interest in developing other types
of semiconductors. Chambers and his team were testing germanium
in combination with a specialized thin crystalline film of lanthanum-strontium-zirconium-titanium-oxide (LSZTO).

"We are reporting on a powerful tool for probing semiconductor structure
and function," said Chambers. "Hard X-ray photoelectron spectroscopy
revealed in this case that atoms of oxygen, an impurity in the germanium, dominate the properties of the material system when germanium is joined
to a particular oxide material. This was a big surprise." Using the
Diamond Light Source on the Harwell Science and Innovation Campus in Oxfordshire, England, the research team discovered they could learn a
great deal more about the electronic properties of the germanium/LSZTO
system than was possible using the typical methods.

"When we tried to probe the material with conventional techniques,
the much higher conductivity of germanium essentially caused a short
circuit," Chambers said. "As a result, we could learn something about the electronic properties of the Ge, which we already know a lot about, but
nothing about the properties of the LSZTO film or the interface between
the LSZTO film and the germanium - - which we suspected might be very interesting and possibly useful for technology." A new role for hard
X-rays The so-called "hard" X-rays produced by the Diamond Light Source
could penetrate the material and generate information about what was
going on at the atomic level.

"Our results were best interpreted in terms of oxygen impurities in the germanium being responsible for a very interesting effect," Chambers
said. "The oxygen atoms near the interface donate electrons to the LSZTO
film, creating holes, or the absence of electrons, in the germanium within
a few atomic layers of the interface. These specialized holes resulted in behavior that totally eclipsed the semiconducting properties of both n-
and p-type germanium in the different samples we prepared. This, too,
was a big surprise." The interface, where the thin-film oxide and the
base semiconductor come together, is where interesting semiconducting properties often emerge. The challenge, according to Chambers, is to
learn how to control the fascinating and potentially useful electric
fields that forms at these interfaces by modifying the electric field
at the surface. Ongoing experiments at PNNL are probing this possibility.

While the samples used in this research do not likely have the immediate potential for commercial use, the techniques and scientific discoveries
made are expected to pay dividends in the longer term, Chambers said. The
new scientific knowledge will help materials scientists and physicists
better understand how to design new semiconductor material systems with
useful properties.

PNNL researchers Bethany Matthews, Steven Spurgeon, Mark Bowden,
Zihua Zhu and Peter Sushko contributed to the research. The study
was supported by the Department of Energy Office of Science. Some
experiments and sample preparation were performed at the Environmental Molecular Sciences Laboratory, a Department of Energy Office of Science
user facility located at PNNL. Electron microscopy was performed in the
PNNL Radiochemical Processing Laboratory. Collaborators Tien-Lin Lee and
Judith Gabel performed experiments at the Diamond Light Source. Additional collaborators included the University of Texas at Arlington's Matt
Chrysler and Joe Ngai, who prepared the samples.

========================================================================== Story Source: Materials provided by
DOE/Pacific_Northwest_National_Laboratory. Original written by Karyn
Hede. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. S. A. Chambers, M. Chrysler, J. H. Ngai, T.-L. Lee, J. Gabel, B. E.

Matthews, S. R. Spurgeon, M. E. Bowden, Z. Zhu,
P. V. Sushko. Mapping hidden space-charge distributions across
crystalline metal oxide/group IV semiconductor interfaces. Physical
Review Materials, 2022; 6 (1) DOI: 10.1103/PhysRevMaterials.6.015002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220301093642.htm

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