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GaN HFET MMICs with integrated Schottky-diode for highly efficient digital switch-mode power amplifiers at 2 GHz

: Maroldt, S.; Quay, R.; Haupt, C.; Kiefer, R.; Wiegner, D.; Ambacher, O.


International journal of microwave and wireless technologies 3 (2011), No.3, pp.319-327
ISSN: 1759-0795
ISSN: 1759-0787
Journal Article
Fraunhofer IAF ()
power amplifier; switch-mode; gallium nitride; mobile communication; integrated diode; MMIC; class-S

This work describes the integration of Schottky diodes into fast GaN MMIC process technology suitable for the realization of switch-mode power amplifier core chips for class-S operation at 2 GHz. With the demonstration of this technology, the so-called third-quadrant issue, which reduces the efficiency in band pass-?-? class-S operation can be diminished on device level. Compared to a hybrid diode assembly, the broadband properties of the amplifier module with on-chip-integrated diode can be improved by the reduction of parasitic losses. The GaN heterostructure field effect transistors (HFETs) with integrated series diode show a cut-off frequency of 28 GHz with drain breakdown voltages exceeding ?100 and +100 V and comparable large signal performance to conventional GaN HFETs at 10 GHz. MMIC core chips for class-D and class-S switch-mode power amplifier modules are demonstrated for the operation at mobile communication frequencies between 0.45 and 2 GHz and signal bit rates up to 8 Gbps. The circuits yield broadband output power levels between 4 and 9 W with efficiencies of up to 80%.