SiGe p-n-p HBTs With 265-GHz fmax, 175-GHz fT, and 3.65-ps Gate Delay

SiGe p-n-p heterojunction bipolar transistors (HBTs) are presented with f_T/f_max values of 175 GHz/265 GHz and a minimum current mode logic ring oscillator gate delay of 3.65 ps. The devices are fabricated in an experimental p-n-p 0.25-μm BiCMOS process environment adopting the transistor design of an advanced n-p-n HBT module. The improved RF performance compared with previously reported p-n-p HBTs was enabled by low-temperature disilane-based epitaxial processes, careful base-profile engineering, the realization of low-ohmic collector and emitter layers, and by avoiding thermal treatments higher than 650 °C between base epitaxy and final RTP.