An InP/InGaAs/InP DHBT with high power density at Ka-band

An InP/InGaAs/InP double heterojunction bipolar transistor was fabricated and its Ka-band power performance characterized. The device employed a 30 nm highly doped InGaAs base, and a 150 nm collector with an InAlGaAs linearly graded at the base-collector junction to prevent current blocking and maintain breakdown voltage. The dc current gain is 28.4 at a current density of JC = 666 kA/cm2 and the breakdown voltage (BVCEO) is larger than 5 V. A submicrometer InP/InGaAs DHBT with an emitter size of 0.6 × 12 μm2 demonstrated a maximum cutoff frequency (fT) of 230 GHz, and a maximum output power density of 3.7 mW/μm2 at 29 GHz.