First Fabrication of GaInAs/InP Buried Metal Heterojunction Bipolar Transistor and Reduction of Base-Collector Capacitance

We report a novel approach for improving the performance of InP-based heterojunction bipolar transistors (HBTs). A buried-metal heterojunction bipolar transistor (BM-HBT), in which tungsten stripes of the same area as the emitter metal were buried in an i-InP collector layer, was fabricated for the first time. The aim in fabricating this structure is to realize a reduction in the total base-collector capacitance (CBCT). In the measurement of microwave S-parameters, CBCT of 10.3 fF was evaluated. The effective base-collector junction area of the BM-HBT was estimated to be 22% that of conventional-HBT considering the difference in collector thickness.