THz InP Integrated Heterojunction Bipolar Transistor Technology for mm-Wave Beam Steering Applications

For future mm-wave and THz use, radio front-ends with high efficiency and high output power are required. High antenna directivity at these frequencies makes beam steering a necessity for many applications such as point-to-point or point-to-multipoint links, high resolution radar and stand-off security applications. Indium phosphide heterojunction bipolar transistors exhibit high breakdown voltage at mm-wave frequencies, enabling high efficiency RF power generation. We have demonstrated an improved monolithically integrated transferred-substrate InP HBT process which exhibits 530GHz fmax and more than 4V breakdown voltage at an emitter width of 400nm, enabling 500GHz oscillator cores. The necessary phase shift for wide angle beam steering may be generated at the subharmonic, which can be realized in SiGe BiCMOS technology. A vertical monolithic or chip-wise integration of subharmonic injection-locked InP HBT oscillator cores with BiCMOS control circuitry is an attractive solution for mm-wave beamforming arrays, which can fit into the lateral design constraint of λ/2 element spacing.