Advanced Down-Scaling Technology and its Physical Mechanism for mm-Wave/ Terahertz GaN HEMTs with High Frequency, Low Noise, and High JFoM

To address the strategic need for solid-state power amplifiers and low-noise amplifiers essential for the future of high-performance 5G/6G communications, GaN HEMTs must combine high-frequency and high-power capabilities with cost-efficiency. By leveraging advanced down-scaling techniques, GaN HEMTs on cost-effective sapphire substrates can achieve remarkable RF performance, W-band power, low noise figures, and an outstanding Johnson's figure of merit (JFoM), making them highly suitable for various 5G/6G applications. For GaN HEMTs with an ultra-scaled source-drain distance of 200 nm, minimal parasitic resistance enabled a noise figure of 1 dB across the 25–35 GHz frequency range. These devices achieved a f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> of 220 GHz and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{f}_{\max}$</tex> of 526 GHz. In a continuous-wave, large-signal load-pull test at 94 GHz (W-band), the HEMTs exhibited a gain of 7.25 dB, with a peak output power of 15.2 dBm for a maximum input power of 9.5 dBm, and a power-added efficiency of 15%. The breakdown voltage reached For GaN HEMTs with a source-drain distance of 5 µm, an exceptional breakdown voltage of 190 V was recorded, along with the f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> of 115 GHz, leading to an extraordinary JFoM of 22 THz.V-the highest reported to date. Our findings underscore that GaN HEMTs on sapphire substrates, utilizing advanced down-scaling technology, can achieve performance levels comparable to state-of-the-art devices on SiC substrates.