Analysis of the surface base current drift in GaAs HBT's
A field-induced degradation mechanism responsible for the surface base current drift in GaAs HBT's is studied on the basis of accelerated life-tests : two stress conditions are applied to HBT's and associated TLM structures. An EDX analysis performed on the base ohmic contact confirms the migration of metallic species which are assessed to spread into the extrinsic base region of AlGaAs/GaAs HBT's. The self-passivated GaInP/GaAs technology is expected to improve the HBT reliability.