There are many reasons why gallium arsenide devices exhibit good reliability, but the primary cause is that quality and reliability is built into the process. But there are several clear advantages for devices manufactured at TriQuint. First of all, the metallizations used are all primarily composed of gold. Gold is more conductive than aluminum used in conventional silicon device processing, and is also less susceptible to electromigration.
Gold also is much less susceptible to corrosion than aluminum.
From a reliability standpoint, gold is clearly a superior metal for integrated circuits. This eliminates the primary failure mechanisms found in MOS devices. Next, the use of dielectrics is fundamentally different in TriQuint GaAs than in typical silicon implementations. So the only remaining function of dielectrics in GaAs is for environmental protection. In fact, except where capacitors are needed, GaAs devices could be manufactured without dielectrics and be completely functional.