Imec is exploring two different routes: one is Indium Phosphide (InP) on Si, targeting mm-wave and frequencies above 100 GHz (future 6G applications) and the other is GaN-based devices on Si, targeting (in a first phase) the lower mm-wave bands and addressing applications in need of high power densities. For both routes, the researchers have now obtained first functional devices with promising performance characteristics while identifying ways to further enhance their operating frequencies
The researchers demonstrated functional GaAs/InGaP HBT devices grown on 300mm Si, obtaining a defect-free device stack with below 3 x 106 cm-2 threading dislocation density using imec’s unique III-V nano-ridge engineering (NRE) process. The devices were shown to perform considerably better than reference devices, with GaAs fabricated on Si substrates with strain relaxed buffer (SRB) layers. Next, the researchers aim to explore higher-mobility InP-based devices (HBT and HEMT).
On a second research path, imec has fabricated CMOS-compatible GaN/AlGaN-based devices on 200-mm Si and compared three different device architectures – HEMTs, MOSFETs and MISHEMTs, concluding that MISHEMT devices outperform the other device types in terms of device scalability and noise performance for high-frequency operation. For 300-nm gate lengths, the researchers measured peak cut-off frequencies of fT/fmax around 50/40 GHz, which is in line with reported GaN-on-SiC devices. They are confident that further gate length scaling could further improve their device performance and increase the operating frequency within the mm-wave bands.