Abstract
In this paper, a high-power amplifier integrated circuit (IC) in gallium-nitride (GaN) on silicon (Si) technology is presented at a W-band (75–110 GHz). In order to mitigate the losses caused by relatively high loss tangent of Si substrate compared to silicon carbide (SiC), low-impedance microstrip lines (20–30 Ω) are adopted in the impedance matching networks. They allow for the impedance transformation between 50 Ω and very low impedances of the wide-gate transistors used for high power generation. Each stage is matched to produce enough power to drive the next stage. A Lange coupler is employed to combine two three-stage common source amplifiers, providing high output power and good input/output return loss. The designed power amplifier IC was fabricated in the commercially available 60 nm GaN-on-Si high electron mobility transistor (HEMT) foundry. From on-wafer probe measurements, it exhibits the output power higher than 26.5 dBm and power added efficiency (PAE) higher than 8.5% from 88 to 93 GHz with a large-signal gain > 10.5 dB. Peak output power is measured to be 28.9 dBm with a PAE of 13.3% and a gain of 9.9 dB at 90 GHz, which corresponds to the power density of 1.94 W/mm. To the best of the authors’ knowledge, this result belongs to the highest output power and power density among the reported power amplifier ICs in GaN-on-Si HEMT technologies operating at the W-band.
Highlights
W-band frequencies, especially higher than 90 GHz, allow for short wavelength and propagation windows for electromagnetic waves
It is worthwhile to emphasize that the W-band power amplifier integrated circuit (IC) mentioned above are based on GaN on silicon carbide (SiC) high electron mobility transistor (HEMT) technologies [1,2,3,4,5,6,7], where a GaN channel is grown on the SiC substrate with a buffer layer in between [4]
They present the superior performance to GaN-on-Si HEMTs, which are grown on the Si substrate, in terms of output power, power density, and power added efficiency (PAE) at all frequency ranges [8]
Summary
W-band frequencies, especially higher than 90 GHz, allow for short wavelength and propagation windows for electromagnetic waves. Instead of the conventional Si-based transistor technologies, the advanced wide-band gap gallium-nitride (GaN) high-electron mobility transistors (HEMTs) are widely adopted in the design of W-band high-power amplifier ICs, because they present high breakdown voltage, which permits high power generation They exhibit a high electron saturation velocity, providing high gain at high frequency [1,2]. It is worthwhile to emphasize that the W-band power amplifier ICs mentioned above are based on GaN on silicon carbide (SiC) HEMT technologies [1,2,3,4,5,6,7], where a GaN channel is grown on the SiC substrate with a buffer layer in between [4] They present the superior performance to GaN-on-Si HEMTs, which are grown on the Si substrate, in terms of output power, power density, and PAE at all frequency ranges [8].
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