GaAs power metal-semiconductor field-effect transistors (MESFETs) were fabricated using direct double silicon (Si) ion implantation technology for wireless communication applications. A 150-µm MESFET had a saturation drain current of 238 mA/mm after Si 3 N 4 passivation. A 15-mm MESFET, when measured under a class-AB condition with a biased drain voltage of 3.4 V and a quiescent drain current of 600 mA, delivered a maximum output power (P out ) of 31.1 dBm and a maximum power-added efficiency

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... AE) of 58.0% at a frequency of 1.88 GHz. The MESFET exhibited a P out of 29.2 dBm with a PAE of 45.0% at the 1-dB gain compression point. The MESFET, when measured under a deep class-B condition with a biased drain voltage of 4.7 V and a quiescent drain current of 50 mA, achieved a maximum P out of 33.1 dBm and a maximum PAE of 55.9% at 1.88 GHz. The MESFET operating at 4.7 V and 1.88 GHz exhibited a P 1dB of 31.8 dBm and an associated PAE of 47.1% at the 1-dB gain compression point. When tested by IS-95 code-division multiple access (CDMA) standard signals and biased at 4.7 V under the deep class-B condition, the MESFET with a P out of 28 dBm demonstrated an adjacent channel power rejection (ACPR) of -31.2 dBc at +1.25 MHz apart from the 1.88 GHz center frequency and -45.7 dBc at +2.25 MHz. This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.