Characterization of InGaP/GaAs HBTs under Temperature and
Tohru Oka, Koji Hirata, Hiroyuki Takazawa, Isao Ohbu
Central Research Laboratory, Hitachi Ltd., Hitachi ULSI Systems
1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan
High-temperature bias stress tests on InGaP/GaAs HBTs are carried out at an emitter-base junction temperature ranging from 360 to 440oC and a collector current density of 1 x 105 A/cm2. The drastic degradation of current gain is caused by the increase in the base current with an ideality factor close to 1, implying that the degradation results from the decrease of the minority carrier lifetime in the neutral base region. The variations in current-voltage characteristics of the emitter-base and base-collector junctions during stress testing reveal that the recombination centers continuously increase in the base layer near the emitter-base junction from the beginning of the bias testing. Both self-aligned HBTs and non-self-aligned HBTs have the same dependence of lifetime on the junction temperature with the same activation energy of 2.0 eV, suggesting that the current gain degradation is related to the intrinsic base region.