- Researchers show a whole new perspective of designing light emitting devices.
- Diamonds can be used to make 100 times brighter light devices than existing LEDs and lasers.
- It could enable fabrication of light sources for Li-Fi and transmitters for the quantum internet.
Many semiconductor devices operate by creating a high density of nonequilibrium carriers under a bias voltage. Such carriers (electrons and holes) are capable of recombining or changing the properties of the semiconductor, and this phenomenon can be exploited for light modulation.
The intensity of light is proportional to the concentration of electrons and holes and how fast they recombine. Modern devices like lasers and LEDs (used in high-speed internet and laser printer) rely on this process.
However, there doesn’t exist a semiconductor that can provide enough concentration of electrons and holes. In the 1960s, scientists came up with a solution – heterostructures that contain two or more semiconductors.
In such heterostructures, a semiconductor is sandwiched between two semiconductors with larger bandgaps. In this way, the middle layer’s concentration of electrons and holes can be increased to a sufficiently high level by applying a forward bias voltage. This effect is called superinjection, and this is how modern LEDs and laser are made.
To make a viable heterostructure, it’s important to select semiconductors that have the same period of the crystal lattice. This results in fewer defects at the interface between the semiconductor, and thus brighter light source.
These heterostructures are difficult to fabricate as compared to homostructures (made of single semiconductor). For years, scientists have been trying to use homostructures to build light sources, but they haven’t achieved any success yet.
Superinjection In Homostructures
Recently, researchers at the Moscow Institute of Physics and Technology published a paper in which they described a whole new perspective of designing light emitting devices.
The paper shows that superinjection can be achieved with just one semiconductor. And the best thing is it can be done by using well-known, already available semiconductors.
At present, silicon and germanium semiconductors are used to make bright light sources, which support superinjection at cryogenic temperatures. However, in the case of gallium nitride and diamond, strong superinjection could occur at room temperature. Their effect could be utilized to produce mass-market equipment.
Illustration of homo- and heterostructures | Credit: MIPT
Superinjection in diamonds can generate 10,000 times higher concentrations than what was assumed to be ultimately possible. Therefore, diamonds can be used as a basis for ultraviolet light emitting diodes thousands of times brighter than the most optimistic previous calculations. Moreover, its effect is up to 100 times stronger than existing semiconductor lasers and LEDs based on heterostructures.
The study makes it possible to inject a high density of electrons into a large volume, enhancing the efficiency of electron injection, which can drastically increase the brightness of single-photon sources and light emitting diodes based on diamond.
According to the researchers, superinjection can occur in various semiconductors, ranging from 2D materials to conventional wide-bandgap semiconductors.
This could enable fabrication of highly efficient violet, ultraviolet, white, and blue LEDs, along with the light sources for Li-Fi (optical wireless communication), optical instruments for early disease diagnostics, transmitters for the quantum internet, and new kinds of lasers.