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/μιη² in order to investigate the stability of InP/InGaAs emitter-base (E-B) junction. At 10 mA/μιη² operation with the junction temperature of 210°C, dc current gain, ß, was stable for 1000 h. The activation energy for the reduction of β, 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.