AlGaAs/GaAs Heterojunction Bipolar Transistors grown on silicon by MOCVD.

We investigated the electrical characteristics of AlGaAs/GaAs Heterojunction Bipolar Transistors grown simultaneously on n and p type silicon substrates. Transistors in a mesa type structure with emitter widths from 1.5 to 6.0micron were fabricated. The DC results indicate that bipolar transistors are not sensitive to growth defects due to the lattice mismatch between GaAs and Si. The dc common emitter current gain averaged a value between 4 and 10, independent of geometry and size of devices (both 1.5 micronx 6micron and 6 micronx 50micron emitter area yield the same results). These are similar to the values obtained in HBTs fabricated by the same process on GaAs substrates grown by MOCVD.