Power and linearity comparisons of gate- and source-terminated field-plate pseudomorphic HEMTs

GaAs-based pseudomorphic high electron mobility transistors (pHEMTs) in which the field-plate (FP) is connected to the gate terminal and the source terminal, were developed and evaluated experimentally to determine their microwave and power performance. The small gate-to-drain feedback capacitance (C_gd) and the stable FP-induced depletion region at high input power (P_in) of the source-terminated FP pHEMT (FP-S pHEMT) greatly improve the power and linearity of the FP-S pHEMT above those of the gate-terminated FP pHEMT (FP-G pHEMT). The power ratio of the fundamental to the third-order inter-modulation product (IM3) is 18.8 dBc for FP-S pHEMT for P_in ≤ 0 dBm; the corresponding value for FP-G pHEMT is 12.4 dBc. These experimental results indicate that the FP architecture is more effective at high-power operation and exhibits high linearity in high-power pHEMT applications.