GaAsSb-Based DHBTs With a Reduced Base Access Distance and $f_{\mathrm {T}}/f_{\mathrm {MAX}}=$ 503/780 GHz

We report InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with simultaneous current and power gain cutoff frequencies of ${f} _{\mathbf {T}}/f_{\mathrm {\mathbf {MAX}}}=$ 503/780 GHz. Devices with a 0.2 $\times $ 4.4 $\mu $ m $^{\mathrm {\mathbf {2}}}$ emitter area feature a peak DC current gain $\beta $ = 17 and a common-emitter breakdown voltage BV $_{\mathrm {\mathbf {CEO}}}$ = 4.1 V. To the best of our knowledge, the present transistors are the first GaAsSb-based DHBTs to feature ${f} _{\mathrm {\mathbf {MAX}}}$ > 750 GHz. The progress in RF performance is enabled by a reduction of the base access resistance and base-collector capacitance achieved via an improved self-aligned emitter etching procedure.