Influence of dislocations on the DC characteristics of AlGaAs/GaAsheterojunction bipolar transistors

The influence of dislocations on the minority electron lifetime in p-type GaAs layers and on AlGaAs/GaAs HBTs has been investigated. The minority electron lifetime in 1×10¹⁹/cm³ doped p-GaAs decreases significantly when the dislocation density is greater than 10⁷/cm². This result agrees well with analysis of carrier transport in highly dislocated material. Current gain reduction in HBTs with high dislocation density is found to be due to two effects: reduction of the electron lifetime in the base layer and an increase of the recombination current in the emitter-base junction depletion region. These two effects are comparable in reducing the current gain