Degradation mechanisms in 2 W MESFETs

Biased life tests and thermal storage at different temperatures have been performed on 2 W GaAs MESFETs from two different suppliers. Failure modes and mechanisms are correlated to device technology and are thermally activated. In samples with Au/Pd/Ti gate metallization we observed a decrease of Idss current and an increase of the gate diode reverse current. The former is related to the gate‐semiconductor interaction, whereas annealing of GaAs surface states is responsible for the latter, which can cause the device burn‐out. These degradations exhibit activation energies of 1 eV and 1.5 eV, respectively. In samples with Al gate metallization, we measured an increase of parasitic resistances possibly deriving from a degradation of the ohmic contacts.