Gate metal interdiffusion induced degradation in space-qualified GaAs PHEMTs

While gate metal sinking has been traditionally identified as the primary degradation mechanism in GaAs pseudomorphic high electron mobility transistors (PHEMTs), there is no physical demonstration of gate metal interdiffusion or understanding of the gate metal interdiffusion effect on reliability performance. This paper reviews our results on gate metal interdiffusion in 0.15-μm GaAs PHEMTs subjected to accelerated temperature lifetest. We used the techniques of focused ion beam (FIB), high-resolution energy-dispersive analysis with X-ray (EDX), and scanning transmission electron microscope (STEM). These results substantiate the observed d.c. and RF parametric evolution with respect to reverse gate leakage current (Ig), ideality factor, Schottky barrier height (ΦBN), transconductance (Gm), Idss, pinchoff voltage (Vpo), S21, and provide insights into the effect of gate metal interdiffusion on reliability performance. The comprehensive understanding of gate metal interdiffusion induced degradation is essential for GaAs PHEMTs due to their widespread military/space applications.