Fabrication of InP/InGaAs DHBTs with Buried SiO2 Wires

In this paper, we report the fabrication and device characteristics of InP/InGaAs double heterojunction bipolar transistors (DHBTs) with buried SiO 2 wires. The SiO 2 wires were buried in the collector and subcollector layers by metalorganic chemical vapor deposition toward reduction of the base-collector capacitance under the base electrode. A current gain of 22 was obtained at an emitter current density of 1.25 MA/cm 2 for a DHBT with an emitter width of 400 nm. The DC characteristics of DHBTs with buried SiO 2 wires were the same as those of DHBTs without buried SiO 2 wires on the same substrate. A current gain cutoff frequency (f T ) of 213 GHz and a maximum oscillation frequency (f max ) of 100 GHz were obtained at an emitter current density of 725 kA/cm 2 .