Higher optoelectronic units could possibly be realized utilizing a high-quality movie of cuprous iodide.
A defect-free skinny movie of cuprous iodide—made up of only one crystal—has been fabricated by RIKEN physicists1. The atomically flat pattern is a lift for producing higher semiconductors.
Semiconductors lie on the coronary heart of many optoelectronic units together with lasers and light-emitting diodes (LEDs). Engineers would love to make use of cuprous iodide—an instance of a halide compound—for semiconductors as a result of it is a wonderful conductor that’s steady above room temperature. The difficulty is that it’s robust to manufacture a genuinely skinny movie of cuprous iodide with out impurities. The same old technique includes depositing the movie from an answer. “However an answer course of can’t make a high-quality skinny movie from cuprous iodide,” says Masao Nakamura of the RIKEN Middle for Emergent Matter Science.
As a substitute, Nakamura and his co-workers used an alternate approach often known as molecular beam epitaxy, during which the movie is progressively grown on prime of a substrate, at an elevated temperature, and in a vacuum. Molecular beam epitaxy is already generally employed in manufacturing semiconductors. However it’s exhausting to make use of for cuprous iodide as a result of the fabric is extremely unstable—which means that it simply evaporates in the course of the course of, moderately than settling into a movie. To beat this issue, the workforce started rising their movie at a decrease temperature after which elevated the temperature. “This two-step course of we newly developed was extremely efficient,” says Nakamura.
The workforce had one other trick to boost the standard of their movie. They selected indium arsenide because the substrate since its lattice spacing is similar to that of cuprous iodide. “If the lattice spacing just isn’t effectively matched, many defects will type within the materials,” explains Nakamura.
Nakamura and his colleagues then examined the purity of their pattern utilizing a way referred to as photoluminescence spectroscopy, which includes firing photons, or particles of sunshine, on the floor of the fabric. These photons are absorbed by the fabric, thrilling its electrons to the next power state and inflicting them to emit new photons (Fig. 1). Monitoring the emitted mild allowed the workforce to find out that they’d created a single-crystal movie, free from defects. “We anticipated the standard to enhance utilizing our technique,” says Nakamura. “However the outcomes exceeded our expectations.”
Nakamura and his workforce now plan to sandwich collectively semiconductors made of various halides and examine new properties that come up. “We are going to discover rising novel functionalities and physics on the halide interfaces,” says Nakamura.
Reference: “Heteroepitaxial progress of extensive bandgap cuprous iodide movies exhibiting clear free-exciton emission” by S. Inagaki, M. Nakamura, Y. Okamura, M. Ogino, Y. Takahashi, L. C. Peng, X. Z. Yu, Y. Tokura and M. Kawasaki, 5 January 2021, Utilized Physics Letters.