Semiconductor Homostructures Could Improve LED Design

Researchers from the Moscow Institute of Physics and Technology (MIPT) have found that superinjection, an effect previously believed to be possible only in semiconductor heterostructures, can also occur in homostructures — that is, in structures made of a single semiconductor material. Most known semiconductors could be used to build homostructures that are capable of superinjection, they said. Their discovery could lead to new approaches in the development and production of light sources.

Homostructures and heterostructures. Courtesy of the MIPT Press Office.

Diamond and many emerging wide-bandgap semiconductor materials show outstanding optical and magnetic properties, the researchers said. However, these materials cannot be doped as efficiently as silicon or gallium arsenide, which has limited their practical applicability.

The MIPT team predicted a superinjection effect in diamond p-i-n diodes that would allow for the injection of orders of magnitude more electrons into the i-region of the diode than doping of the n-type injection layer would allow.

The team believes superinjection could produce electron concentrations in a diamond diode that are 10,000x higher than those previously thought possible. As a result, the researchers said, diamond could potentially serve as the basis for UV LEDs thousands of times brighter than what theoretical calculations now predict to be possible. “Surprisingly, the effect of superinjection in diamond is 50 to 100x stronger than that used in most mass-market semiconductor LEDs and lasers based on heterostructures,” researcher Igor Khramtsov said.

According to researcher Dmitry Fedyanin, “In the case of silicon and germanium, superinjection requires cryogenic temperatures, and this casts doubt on the utility of the effect. But in diamond or gallium nitride, strong superinjection can occur even at room temperature."

Superinjection should be possible in a wide range of semiconductors, they said, from conventional wide-bandgap semiconductors to novel 2D materials. This could open the way for new methods to design highly efficient blue, violet, UV, and white LEDs, as well as light sources for optical wireless communication (Li-Fi), new types of lasers, transmitters for the quantum internet, and optical devices for early disease diagnostics.

The research was published in Semiconductor Science and Technology (https://doi.org/10.1088/1361-6641/ab0569).