As a result, researchers worldwide are trying to find ways to boost the amount of light that ultrathin semiconductors can absorb. Harvard University researchers recently had varying degrees of success by combining thin films of germanium, another common semiconductor, on a gold surface.
"While the results are impressive, gold is among the most expensive metals," said Suhua Jiang, associate professor of materials science at Fudan University in China. "We illustrated a nanocavity, made with aluminum or other whitish metals and alloys that are far less expensive, can be used to increase the amount of light that semiconducting materials absorb."
The nanocavity consists of, from bottom to top: aluminum, aluminum oxide and germanium. In the experiment, light passed through the germanium, which is 1.5 to 3 nanometers thick, and circulated in a closed path through the aluminum oxide and aluminum.
The absorption rate peaked at 90 percent, with germanium absorbing roughly 80 percent of the blue-green light and aluminum absorbing the rest. This is ideal, said Haomin Song, PhD candidate in electrical engineering at UB and the paper's first author, because the bulk of the light stays within the semiconducting material.
"The nanocavity has many potential applications. For example, it could help boost the amount of light that solar cells are able to harvest; it could be implanted on camera sensors, such as those used for security purposes that require a high-speed response. It also has properties that could be useful for photocatalytic water splitting, which could help make hydrogen fuel a reality," Song said.
Before any of that happens, however, more research must be done, especially as it relates to how the semico
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University at Buffalo