Composition- and Doping-Graded-Base InP/InGaAsSb Double Heterojunction Bipolar Transistors Exhibiting Simultaneous \(f_{t}\) and \(f_{\textrm {max}}\) of Over 500 GHz

We demonstrate composition- and doping-graded-base InP/InGaAsSb double heterojunction bipolar transistors (DHBTs) with a passivation ledge fabricated in a self-aligned process with i-line lithography. We obtained a high current gain of 52 and high breakdown voltage of 5 V for 0.2-μm-emitter DHBTs featuring 30-nm-thick composition- and doping-graded InGaAsSb base and 100-nm-thick InP collector. The HBTs exhibit an f
_t
of 501 GHz and an f
_max
of 503 GHz at a collector current density of 10.6 mA/μm
²
.