Highly Efficient InP/GaAsSb DHBTs With 62% Power-Added Efficiency at 40 GHz

We report the large-signal load-pull characterization of InP/GaAsSb double heterojunction bipolar transistors (DHBTs) with f
_T
and f
_MAX
cutoff frequencies as high as 380 and 320 GHz, respectively. Measurements were performed at 40 GHz in a passive load-pull system to characterize the output power and power-added-efficiency (PAE) performance. A PAE of 60% with an output power of 10 dBm (corresponding to power densities of approximately 870 mW/mm and 1.45 mW/μm
²
) was achieved in class AB operation. This excellent performance can be attributed to the low offset and knee voltages associated with the InP/GaAsSb type-II heterojunctions. To the best of our knowledge, the present performance exceeds published state-of-the-art results for HBTs at a frequency of 40 GHz.