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

摘要

The reliability of InGaP/GaAs heterojunction bipolar transistors, whose base layer was doped with C to 1 x 10~20 cm~-3, was investigated at an emitter current density J_E of 1 and 2 x 10~5 A/cm~2. The bias stress with J_E=2 x 10~5 A/cm~2 increased emitter resistance R_E, but that with J_E=1 x 10~5 A/cm~2 did not change R_E even at a base-emitter junction temperature T_j of 275 deg 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 x 10~4 h was extrapolated at T_j=125 deg C when J_E=1 x 10~5 A/cm~2.