Advancing high-frequency communication: Scaled InP HBT transistors with fmax> 500 GHz
Fig. 1: SEM image of a processed transistor.
Fig. 2: DC (left) and RF (right) characteristics of the 400 nm transistor technology.
The rapid evolution of mm-wave Monolithic Microwave Integrated Circuits (MMICs) has been driven by an ever-growing demand for high-speed data rates. To overcome data loss over larger communication distances, relatively high output powers and energy efficiencies at frequencies well above 100 GHz are essential, more importantly the D-band (from 140 to 170 GHz). III-V-based technologies offer a solution to this tight-roped compromise between power and efficiency, with InP based heterojunction bipolar transistors (HBTs) being the front runners in this race.
At FBH, we have now taken a significant step forward in this domain. Continuous technological downscaling at our InP MMIC has allowed us, for the first time, to demonstrate a highly scalable InP 400 nm process. Key to this advancement is low ohmic contact resistance and a novel mesa digital etching process. This approach allows for accurate control of the device’s critical dimension, resulting in homogenous device characteristics across the entire wafer. The transistor process utilizes the triple-mesa approach to process the devices with optimal thermal and transistor layout as seen in Fig. 1.
The resulting transistors exhibit remarkable electrical and thermal properties. The direct current (DC) behaviour shows high current density and minor thermal loading up to 2 V VCE, highlighting the robustness under operating conditions. The radio frequency (RF) performance extrapolates an fmax of 530 GHz as seen in Fig. 2.
These advancements offer tangible benefits for next-generation high-frequency systems, including improved data rates, enhanced energy efficiency, and better scalability for future applications.
The current activities were a part of the Key Digital Technologies Joint Undertaking HiCONNECTS project (Project 101097296).
Publication
H. Yacoub et al., “InP-HBT MMIC for RF Applications: Technology Roadmap and Heterointegration”, GEMIC 2025 (accepted for publication).