AlGaN/GaN high electron mobility transistors on semi-insulating bulk ammonothermal GaN have been investigated. By application of regrown ohmic contacts, the problem with obtaining low resistance ohmic contacts to low-dislocation high electron mobility transistor (HEMT) structures was solved. The maximum output current was about 1 A/mm and contact resistances was in the range of 0.3–0.6 Ω·mm. Good microwave performance was obtained due to the absence of parasitic elements such as high access resistance.

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This paper describes the development of a power amplifier operating over a 2.4–2.5 GHz frequency range with the output power level more than 15 W and 60% PAE. The transistor applied was the 10 W (13 W Psat) power GaN HEMT (CGH40010F from Wolfspeed) recommended up to 6 GHz. A harmonic tuning method was used to achieve even 30% more output power than the CGH40010 transistor was specified to deliver while maintaining high gain and high efficiency. Furthermore, an accuracy analysis of amplifier design was also conducted. It included validation and correction of the available transistor models as well as validation of the models of microstrip circuits implemented in ADS. Finally, it was concluded that both the mentioned sources of errors contributed at a similar level.

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