Reliability investigation of heavily C-doped InGaP/GaAs HBTs operated under a very high current-density condition

Abstract

The reliability of InGaP/GaAs heterojunction bipolar transistors, whose base layer was doped with C to 1×10 20 cm −3, was investigated at an emitter current density J E of 1 and 2×10 5 A/cm 2. The bias stress with J E=2×10 5 A/cm 2 increased emitter resistance R E, but that with J E=1×10 5 A/cm 2 did not change R E even at a base-emitter junction temperature T j of 275°C. Bias stress also increased base current I B. An ideality factor of 1.8 for the increased I B indicates that a generation-recombination process in the emitter depletion region dominated the increase in I B under the low injection condition. The increase in I B under the high injection condition indicates that the minority carrier lifetime in the neutral base region decreased with the bias stress. The activation energy for the current gain degradation due to this I B increase under the high injection condition was 1.1 eV. A fairly long lifetime of 8.8×10 4 h was extrapolated at T j=125°C when J E=1×10 5 A/cm 2.