The key term in integrated circuits is integrated. The ability of manufacturing equipment to integrate things limits what processes are available and what materials can be used safely. Once you suggest another material or process, the entire chain is broken and anyone who suggests it should expect people to question your suitability for your current position. "Compatibility" is the reason why you won't find laser-controlled integrated circuits in your laptop.
However, the ability to manufacture lasers using integrated circuit compatible materials may have received a boost as glowing (but not yet lasered) silicon has been demonstrated.
Look on the good side
Optics and lasers are the backbone of high-speed data transmission. They do not use copper wires to transport data at 1 TB / s. Instead, use glass and some fine-tuned and very expensive laser diodes. However, laser diodes are manufactured using methods and materials that are incompatible with those used to manufacture integrated circuits. So while it is possible, for example, to establish an optical connection between a RAM module and a CPU, you have to somehow glue the optics in exactly the right place on the silicon chip. Research laboratories like to sacrifice doctoral students for such ventures, but PhD bots don't scale well, are maintenance-intensive, and their use results in a dark appearance.
A better solution would be to get silicon to emit light, but it really doesn't like it. The reason is not that complicated, but it takes a few words to explain it.
Light is generated by charged particles, such as electrons, that emit energy to emit a photon. In a semiconductor, electrons cannot have some old energy – they must have an energy that is allowed by the structure of the material. The available electron states in semiconductors are limited, which can lead to problems. For example, an electron could have a fairly old piece of energy but could not emit it because all lower energy states are already occupied by electrons.
The situation is even darker because states are defined by more than their energy; Their properties include momentum, angular momentum and more. So an electron may have an energy state with low energy, but the electron cannot enter this state directly because it has the wrong impulse.
This is exactly the problem that electrons face in silicon. An electron can be excited and should emit a photon in the near infrared to get rid of its excess energy. However, all available low energy states require that the electron simultaneously emit a photon and change the momentum (usually by bouncing off a silicon atom). Since this combination is highly unlikely, the electron just jumps around and loses both energy and momentum due to collisions.
Materials in which electrons cannot easily overcome energy barriers are called semiconductors with an indirect band gap. Very little light is emitted in these semiconductors.
Silicon is not the only material like this. The researchers were inspired by the behavior of his close relative germanium, which has also not been elucidated. If the crystal structure (the way the germanium atoms are arranged) of germanium changes, the electrons can emit photons without having to change the momentum. In other words, the band gap changes from indirect to direct depending on the material structure.
In order to make silicon glow, the researchers turned to alloys. A cool thing about semiconductors is that their optical and electronic properties change slightly when alloyed. When you add silicon germanium, the resulting alloy shows some of the properties of germanium. While some properties can be adjusted continuously, others cannot. A band gap is either direct or indirect, not a mix. So how much germanium do you need to make silicon glow?
The answer is 65 percent.
To determine this number, the researchers grew nanowires from silicon-germanium alloys. The nanowires allowed them to choose a template material that forced the silicon germanium alloy to form the correct crystal structure to form a band gap. It also enabled the researchers to compare crystalline structures of different quality.
The researchers' experiments have put quality in the spotlight: the nanowires had to be almost perfect to get an adequate amount of light out of them. All crystals have defects (gaps or dislocations) and high quality crystals have less. Once the researchers had perfected the manufacture of the nanowires, the produced ones would emit a surprisingly large amount of light.
The amount of light is small compared to mature laser diode technology, but still bright compared to what was previously available. The shiny silicon seems to show a practicable way to place all the elements required for optical communication on a silicon chip. This means that communication with peripheral devices such as storage, hard drives and more can be faster. This also means that things like on-chip clock synchronization are easier to organize. However, for this to happen, the researcher's faint glow wire must burn onto the list of acceptable factory materials.
Nature, 2020, DOI: 10.1038 / s41586-020-2150-y (About DOIs)