INFLUENCE OF BASE THICKNESS ON COLLECTOR BREAKDOWN IN ABRUPT ALINAS/INGAAS HETEROSTRUCTURE BIPOLAR-TRANSISTORS

We have studied the effect of base thickness on impact ionization in the collector of In0.53Ga0.47As heterostructure bipolar transistors (HBT’s) with abrupt Al0.48In0.52 As emitters. When the base thickness is less than the mean-free path for energy relaxation in the base, the avalanche process in the collector is enhanced by high-energy injection from the emitter. On the other hand, no such dependence is observed for long-base transistors with equilibrium base transport. These effects are expected as the emitter injection energy of 0.48 eV is appreciable compared to the impact ionization threshold of 0.83 eV in the InGaAs collector. © 1990 IEEE