Improved reliability of AlGaAs/GaAs heterojunction bipolar transistors with a strain-relaxed base

The authors reveal a key to improving the life of MOCVD-grown AlGaAs/GaAs heterojunction bipolar transistors with carbon-doped base. In addition to presenting new findings on current gain degradation properties, it is shown that the importance of lattice strain relaxation in a carbon-doped base layer. Indium was incorporated into C-doped GaAs to relax strain by controlling the lattice constant in the base layer, which was slightly shrunk by carbon doping. Although lifetime testing is still underway, the median life is estimated to be longer than 2.8 /spl times/ 10/sup 6/ hours and 1.1 /spl times/ 10/sup 5/ hours where the collector current density is 10 kA/cm/sup 2/and 50 kA/cm/ /sup 2/, respectively.<
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