Degradation mechanisms induced by high current density in Al-gate GaAs MESFET's

High gate-current density, which can arise due to RF overdrive, induces two degradation mechanisms in Al-gate power GaAs MESFET's: 1) high current density through the Al-gate finger section causes gate interruption at the beginning of the metal stripe due to electromigration and makes it impossible to reach the pinchoff condition; 2) high current density through the Schottky junction promotes a fast Al/GaAs interaction, causing an increase in the Schottky-barrier height from 0.80 to 0.96 eV owing to the formation of an Al
x
Ga
1-x
As interfacial layer. Al/GaAs interaction appears to be enhanced by the electron current at a given temperature.