Researchers at the University of California, Santa Barbara have achieved the first ever “video” of a charge passing through an interface between two different semiconductor materials. Using scanning ultrafast electron (SUEM) technology developed in Bolin Liao’s lab, the researchers were able to directly visualize this fleeting phenomenon for the first time.
“There are many textbooks written about this process based on semiconductor theory,” says Liao, an associate professor of mechanical engineering. “There are a lot of indirect measurements.” The ability to visualize how this process actually happens will allow semiconductor materials scientists to benchmark some of these theories and indirect measurements, he said. added.
This research Proceedings of the National Academy of Sciences.
“Hot” photo carrier
If you’ve ever used solar cells, you’ve probably seen photocarriers in action. When sunlight hits a semiconductor material, electrons within the material are excited and move. This movement of electrons and their separation from oppositely charged “holes” generates an electrical current that can be used to power electronic devices.
However, these photocarriers lose most of their energy within picoseconds (trillionths of a second), so the energy that traditional solar power collects is lost until these carriers cool and release most of their energy. It’s only a fraction of the energy you have in the previous “hot” state. Excess energy is exhausted as waste heat. While high-temperature conditions offer many possibilities in terms of energy efficiency, etc., they also create challenges within semiconductor materials, such as heat, which can impact device performance.
As a result, it is important to better understand how these hot carriers behave as they move through different semiconductor materials, especially at the interface, or heterojunction, of two different materials. . In the realm of semiconductor materials, heterojunctions affect the movement of charge carriers for a variety of purposes, from laser creation to photovoltaics, sensors, and photocatalysis.
