Imec Advances GaN-on-Si and InP-on-Si Technologies for Next-Gen Wireless Communication

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Imec, a leading research and innovation hub in nanoelectronics and digital technologies, is making significant progress in developing the next generation of wireless communication technologies. With the increasing demand for faster and more efficient data transfer, researchers are looking beyond the current fifth-generation (5G) mobile communication to envision the sixth-generation (6G) networks, which are projected to operate at peak data rates of 100Gbit/s from 2030 onwards.

www.everythingrf.com/, Jul. 04, 2023 – 

To enable these exceedingly high data rates, the telecom industry has been pushing up the frequencies of wireless signals. While 5G initially uses sub-6GHz frequency bands, products targeting 28/39GHz are already showcased. Additionally, there is a growing interest in using FR3 (6-20GHz) frequency bands for 5G networks due to their ability to balance coverage and capacity.

Moving toward higher frequencies has several advantages: new frequency bands can be used, solving the spectrum scarcity issue within existing bands. Also, the higher the operating frequency, the easier it is to obtain wider bandwidths. Frequencies above 100GHz and bandwidths up to 30GHz allow telecom operators, in principle, to use lower-order modulation schemes within the wireless data links, which reduces power consumption. Higher frequencies are also associated with smaller wavelengths (λ). As the antenna array size scales with λ², antenna arrays can be packed more densely. This contributes to better beamforming, a technique that ensures that a larger fraction of transmitted energy reaches the intended receiver.

But the advent of higher frequencies comes at a price. Today, CMOS is the preferred technology for building the critical components of transmitters and receivers. These include the power amplifiers within the front-end modules that send the radio frequency signals to and from the antennas. The higher the operating frequency, the more the CMOS-based power amplifiers struggle to deliver the required output power with sufficiently high efficiency.

And that's where technologies such as GaN and InP come into play. Due to outstanding material properties, these III/V semiconductors are more likely to provide the required output power and efficiency at high operating frequencies. GaN, for example, has a high current density, high electron mobility, and large breakdown voltage. The high power density also allows for a small form factor and, thus, a reduction in overall system size at the same performance.

Imec conducted a modeling exercise to compare the performance of different power amplifier implementations at an operating frequency of 140GHz. The results showed that InP-based power amplifiers outperformed CMOS-based and CMOS beamformer with SiGe heterojunction bipolar transistor (HBT) implementations in terms of output power and energy efficiency. GaN-on-silicon-carbide (GaN-on-SiC) high-electron-mobility transistors (HEMTs) also demonstrated excellent performance at lower millimeter-wave frequencies (28 and 39GHz) compared to CMOS-based devices and GaAs HEMTs. In this exercise, two different use cases were considered, i.e., fixed wireless access (FWA, with 16 antennas) and user equipment (with four antennas).

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