InP/GaInP Composite-Collector for Improved Breakdown Voltage in the InP/GaAsSb DHBTs

We demonstrate the use of a composite InP/GaInP collector to enhance the breakdown voltage of InP/GaAsSb double heterojunction bipolar transistors (DHBTs). The common-emitter breakdown voltage $BV_{\text{CEO}}$ increased from 4.1 V in a DHBT with a pure InP collector to 4.5 V in a DHBT with a composite collector. This increase in breakdown voltage is achieved without compromising the RF performance. The $(0.15\times 7.5)\mu\mathrm{m}^{2}$ composite-collector DHBTs show a simultaneous $f_{\mathrm{T}}/f_{\mathrm{MAX}}=470/808\mathrm{GHz}$.