Engineers at the University of California San Diego used metamaterials to develop the world's first semiconductor-free, light-controlled microelectronic device that was only excited by low-voltage, low-power lasers. The conductivity is 10 times higher than the conventional one. This technology is conducive to the manufacture of faster, higher power microelectronic devices and is expected to produce more efficient solar panels.

The performance of existing conventional microelectronic devices, such as transistors, is ultimately limited by the performance of their constituent materials. For example, the nature of the semiconductor itself limits the conductivity or electron flow of the device. Because semiconductors have a so-called band gap, this means that some external energy needs to be applied to cause electrons to jump through the band gap. In addition, the electron velocity is also limited because when electrons pass through the semiconductor, they always collide with atoms inside the semiconductor.

The Applied Electromagnetics Group, led by Dan Sievenpiper, a professor of electrical engineering at UC San Diego, explored the limitations of using space free electrons to replace semiconductors to overcome the limitations of traditional electronics. Ebrahim Forati, the first author of the study, said: "And, we hope to achieve it on the micro level."

However, the process of releasing electrons from materials is challenging. This process either requires the application of a high voltage (at least 100 volts) and a high power UV laser, or requires extremely high temperatures (over 1000 degrees Fahrenheit), which is impractical on micron and nanoscale electronic devices.

Scanning electron microscope (SEM) image of a semiconductor-free microelectronic device (top left) and its Au superficial surface (upper right, lower)

To cope with this challenge, the West Piper team designed a photo-emissive micro-device that can release electrons from the material, and the release conditions are less demanding.

The device consists of a silicon substrate, a silicon dioxide barrier, and an engineered surface on top of which is called a "metasurface." The surface of the spectacles consists of a parallel strip of Au (gold) arrays and a mushroom-like Au nanostructure array thereon.

The Au Meta surface is designed to produce "hot spots" with high-intensity electric fields when applying DC low voltage (less than 10 volts) and low-power infrared lasers simultaneously. These "hot spots" The energy is enough to "pull" the electrons out of the metal, releasing free electrons.

Device test results show that its conductivity is increased by 10 times. Ibrahim said: "This means that you can control more free electrons."

Western Piper said: "Of course, this will not replace all semiconductor devices, but for some specific applications, this may be the best solution, such as high frequency or high power devices."

According to the researchers, the current Au super-superior surface is only a proof-of-concept design. For different types of microelectronic devices, different super-surface designs and optimizations are needed. Researchers say the next step is to understand the scalability of these devices and the limitations of their performance. ”

In addition to electronics applications, the team is exploring other applications of the technology, such as photochemistry, photocatalysis, etc., in order to achieve new photovoltaic devices or environmental applications.