Avoiding and Leveraging Defects in Thin Films for Next-Generation Technologies
Newswise — WASHINGTON, D.C., Oct. 23, 2018 -- The next generation of phones, computers and wearable devices requires materials that can meet extraordinary demands. Engineers and physicists aim to meet these needs by developing new materials that can perform faster while using less energy.
During the 65th AVS International Symposium and Exhibition, being held Oct. 21-26, in Long Beach, California, researchers will discuss different techniques, from evaporating germanium to creating strategic voids, to improve the electrical performance of succeeding technologies. The researchers will present their findings during the session entitled Electronic Materials and Photonics Division.
Mahmut Kavrik, a doctoral candidate at the University of California, San Diego, is examining how to grow oxides of two elements found in the same group on the periodic table -- silicon and germanium -- without defects at the interface. His goal is to enhance the carrier mobility of a semiconductor.
Past attempts have failed due to the degradation of germanium oxide, resulting in defects in the semiconductor’s oxide interface. These defects trap electrons and prevent them from moving through the material efficiently, ultimately limiting the functionality of the semiconductor.
To Kavrik’s surprise, he found it was possible to grow a silicon germanium-oxide film almost free of defects that was incredibly thin (less than 0.5 nanometers). During this presentation, he will discuss how he achieved this outcome using ozone as a selective oxidation method.
“This [outcome] is nonintuitive,” he said. “It resembles [the process of] slow cooking a steak, which removes the fat and leaves the meat.” Kavrik employed multiple analytical techniques in different labs to verify the results of his approach.
Kavrik used ozone to oxidize silicon and germanium simultaneously on the surface of a material. The silicon oxidized preferentially, while the germanium oxide that formed continued to degrade at the interface, but the degraded germanium evaporated or migrated upward out of the matrix. While the germanium oxide enriched the overlying oxide layer, the defects along the thin-film interface decreased.
These results are encouraging, but Kavrik cautions that more experiments are necessary to see if the germanium oxide continues to migrate within the oxide layer, especially during device operation.
While Kavrik is growing defect-free thin films to enhance carrier mobility of semiconductors, Rachael Myers-Ward, an electrical engineer at the U.S. Naval Research Laboratory in Washington, D.C., is working to spin the defects in a thin film to her advantage.
Researchers have long studied silicon carbide thin films for power electronics because this material exhibits tunable electronic properties as well as thermal and radiation stability. More recently, the presence of point defects, specifically silicon vacancies, offer an appealing option for quantum computing and sensing applications. The vacancies have a relatively unique long electron spin (spin = 3/2) coherence time, which enables a wide range of quantum bit (qubit) and sensor applications. Myers-Ward decided to tune these defects to improve photon emission for improved qubit application.
She has successfully grown a photonic crystal of silicon carbide on a transferable graft. To fabricate the photonic crystals, she explored a new technique called remote epitaxy, which enables the transfer of silicon carbide to silicon dioxide for functional applications. Within the crystal, she plans to position the silicon vacancies using the previously developed techniques of electron irradiation or implantation to enhance photon emission from the silicon carbide.
“I have only been working on this [process] for a few months, and I have already been able to improve surface morphology to grow and transfer a single crystal,” said Myers-Ward. “The possibilities for this technique and what it has to offer make it very exciting research.”
At this point, the results are still limited to small samples. More work is required to determine how to scale the process to a 4-inch wafer and develop techniques to transfer the crystals on grafts for real-world applications.
Presentation 1746, “Suppression of Electronic Defects at HfO2-SiGe Interface with Selective Surface Oxidation Using Ozone,” by Mahmut Kavrik, is at 9:40 a.m. PT, Monday, Oct. 22, 2018, in Room 101A at the Long Beach Convention Center, Long Beach, California.
Presentation 1673, “Processing of Cavities in SiC Material for Quantum Technologies,” by Rachael Myers-Ward, is at 5:40 p.m. PT, Tuesday, Oct. 23, 2018, in Room 101A at the Long Beach Convention Center, Long Beach, California.
MORE ABOUT THE AVS 65TH INTERNATIONAL SYMPOSIUM & EXHIBITION
The symposium is being held Oct. 21-26, 2018, in Long Beach, California.
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