The Effect of Gate Current on the Degradation of GaAs PHEMT MMICs

Scanning transmission electron micrographs were used to investigate the gate metal sinking effect in 0.15 ?m GaAs PHEMT MMICs subjected to elevated temperature lifetesting. Gate metal sinking causes a decrease of the Schottky barrier height, therefore reducing the Schottky diode's forward turn-on voltage. The progressive gate metal sinking eventually leads to a drastic increase in the three-terminal forward gate current. Accordingly, a distinct degradation phenomenon in MMICs due to high forward gate current and gate resistors was observed. The degradation causes a decrease in transconductance and small signal gain, following the earlier gate sinking. In conclusion, a dependence of DC performance and small signal gain on the forward gate current was observed in GaAs PHEMT MMICs.