RELIABILITY STUDY ON InP/InGaAs EMITTER-BASE JUNCTION FOR HIGH-SPEED AND LOW-POWER InP HBT

The reliability of sub-micrometers InP-based heterostructure bipolar transistors (HBTs), which are being applied in over-100-Gbit/s ICs, was examined at high current injection conditions. These HBTs had a ledge structure and an emitter electrode consisting with a refractory metal of W, which suppressed surface degradation and metal diffusion, respectively. We conducted bias-temperature (BT) stress tests in several stress conditions of current densities, J(c), up to 10 mA/mu m(2) in order to investigate the stability of InP/InGaAs emitter-base (E-B) junction. At 10 mA/mu m(2) operation with the junction temperature of 210 degrees C, dc current gain, beta, was stable for 1000 h. The activation energy for the reduction of beta, however, decreased to 1.1 eV, which is suggesting the degradation of the emitter-base (E-B) junction. For the reliability of sub-micrometer, high-speed and low-power InP HBTs at high current densities, stability around the E-B junction has become more dominant.