Intermodulation Distortion in GaN HEMT (Band 8)

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This work treats intermodulation distortion performance of
GaN-HEMT high-power transistors. A detailed study on the physical
parameters influencing third-order intermodulation distortions is
carried out, based on the large-signal model and on physical device
simulation. Devices are characterized in terms of linearity by setting
up a sophisticated measurement system. Among others, an electronic
fuse is used at the drain side to avoid catastrophic failure during
measurement. The bias-dependent transconductance characteristic is
identified as the dominating source for intermodulation distortion in
GaN HEMTs, while drain-source capacitance and access resistances
have only minor influence. The corresponding physical parameters
governing the transconductance behavior are determined and
optimized structures for high linearity are proposed. Besides
characterization and analysis of conventional designs, a novel device
architecture for very high linearity is presented. Finally, performance
of GaN HEMTs within a hybrid amplifier configuration is shown and
the combination of high power, high linearity, and low-noise
characteristics is highlighted.