The effect of passivation on the hot electron degradation of lattice-matched InAlAs/InGaAs/InP HEMTs

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Abstract
Our results indicate that under hot electron conditions both SiN-passivated and bare InP HEMTs have a tendency to degrade from the point of view of dc and rf characteristics. Passivated devices show a permanent decrease of drain current and transconductance at high gate bias. The degradation is attributed to negative charge accumulation at the surface leading to cap depletion, and tends to be weaker in selectively etched gate devices, where the cap is laterally etched away much more. This dc effect is mirrored by a reduction of the current gain cutoff frequency in the same bias range. Bare HEMTs display a variety of degradation modes, depending on the particular device geometrical and process features. The gate recess process, as can be expected, is particularly critical from this standpoint.