A comparison of In0.5Ga0.5P/GaAs:C single and double-heterojunction bipolar transistors grown by LP-MOCVD

Summary form only given. The authors present a comparison of single- and double-heterojunction devices formed in the InGaP/GaAs materials system. The HBT (heterojunction bipolar transistor) structures used for this study were grown by LP-MOCVD (low-pressure metal-organic chemical vapor deposition) using CCl₄ as the base dopant. It was found that the use of a 25-Å spacer layer provided the highest gains in these device structures, with β_MAX~210. A decrease in current gain with increasing spacer layer thickness was attributed to space-charge recombination current at the emitter-base junction. Despite the small conduction band discontinuity reported for this materials system, the gains for the double-heterojunction transistors were considerably lower (β_MAX~25) than for single-heterojunction devices for which all other layers besides the collector were identical. BV_CEO and BV_CBO are, however, significantly higher for InGaP collector structures (22 and 25 V as compared with 9.5 and 18 V for a GaAs collector, respectively)