600 GHz InP/GaAsSb/InP DHBTs Grown by MOCVD with a Ga(As,Sb) Graded-Base and fT x BVCEO ≫ 2.5 THz-V at Room Temperature

We describe the realization of ternary base InP/Ga(As,Sb) DHBTs, where the grading is implemented by ramping the base As/Sb composition ratio from the collector to the emitter side: this enables a cutoff frequency f_T of 603 GHz at room temperature with a breakdown voltage BV_CEO = 4.2 V, for a record f_TxBV_CEO product of 2.53 THz-V. Device performance improves further with cooling to reach f_T ≫ 700 GHz with BV_CEO= 4.4 V at 5K. To the best of our knowledge, this represents the highest f_T ever reported for a DHBT of any kind. The f_TxBV_CEO ≫ 3.10 THz-V at 5 K is also unprecedented.