Up until now, scaling down transistors and other components has been the key to making electrical gadgets faster. But this strategy is at its limit because the advantages of shrinking are outweighed by negative consequences like increased resistance and decreased output power.
Elison Matioli of the Power and Wide-band-gap Electronics Research Lab (POWERlab) in EPFL’s School of Engineering explains that further miniaturization is therefore not a viable solution to better electronics performance.
“New papers come out describing smaller and smaller devices, but in the case of materials made from gallium nitride, the best devices in terms of frequency were already published a few years back,” he says. “After that, there is really nothing better, because as device size is reduced, we face fundamental limitations. This is true regardless of the material used.”
As a solution to this problem, Matioli and PhD candidate Mohammad Samizadeh Nikoo developed a novel strategy for electronics that could get beyond these restrictions and open the door to a new category of terahertz devices.
They altered their device instead of shrinking it, most notably by etching metastructures patterned contacts at sub-wavelength distances onto a semiconductor consisting of gallium nitride and indium gallium nitride. These metastructures give rise to exceptional properties that do not arise naturally by allowing the electrical fields inside the device to be regulated.
This new technology could change the future of ultra-high-speed communications, as it is compatible with existing processes in semiconductor manufacturing. We have demonstrated data transmission of up to 100 gigabits per second at terahertz frequencies, which is already 10 times higher than what we have today with 5G.
Samizadeh Nikoo
Crucially, the device can operate at electromagnetic frequencies in the terahertz range (between 0.3-30 THz) significantly faster than the gigahertz waves used in today’s electronics. They therefore have far higher potential for applications in 6G communications and beyond because they can carry significantly more data for a given signal or time.
“We found that manipulating radiofrequency fields at microscopic scales can significantly boost the performance of electronic devices, without relying on aggressive downscaling,” explains Samizadeh Nikoo, who is the first author of an article on the breakthrough recently published in the journal Nature.
Record high frequencies, record low resistance
This region is frequently referred to as the “terahertz gap” because terahertz frequencies are too rapid for existing electronics to handle and too sluggish for optics applications. A method from the field of optics is to manipulate terahertz waves using sub-wavelength metastructures. Yet in contrast to the optics approach, which involves beaming an external beam of light onto an established design, the POWERlab’s approach enables an unprecedented level of electronic control.
“In our electronics-based approach, the ability to control induced radiofrequencies comes from the combination of the sub-wavelength patterned contacts, plus the control of the electronic channel with applied voltage. This means that we can change the collective effect inside the metadevice by inducing electrons (or not),” says Matioli.
While the most advanced devices on the market today can achieve frequencies of up to 2 THz, the POWERlab’s metadevices can reach 20 THz. Similar to this, current devices working in the terahertz band tend to malfunction at voltages lower than 2 volts, but the metadevices can withstand voltages of more than 20 volts. This makes it possible to transmit and modulate terahertz signals at far higher powers and frequencies than are presently feasible.
Integrated solutions
As Samizadeh Nikoo explains, modulating terahertz waves is crucial for the future of telecommunications, as the increasing data requirements of technologies like autonomous vehicles and 6G mobile communications are fast reaching the limits of today’s devices.
The electronic metadevices developed in the POWERlab could form the basis for integrated terahertz electronics by producing compact, high-frequency chips that can already be used with smartphones, for example.
“This new technology could change the future of ultra-high-speed communications, as it is compatible with existing processes in semiconductor manufacturing. We have demonstrated data transmission of up to 100 gigabits per second at terahertz frequencies, which is already 10 times higher than what we have today with 5G,” Samizadeh Nikoo says.
To fully realize the potential of the approach, Matioli says the next step is to develop other electronics components ready for integration into terahertz circuits.
“Integrated terahertz electronics are the next frontier for a connected future. But our electronic metadevices are just one component. We need to develop other integrated terahertz components to fully realize the potential of this technology. That is our vision and goal.”
