Fabrication and nonlinear characterization of GaN HEMTs on SiC and sapphire for high-power applications

In this work, we present the characterization results for several HEMT GaN-based devices developed by SELEX Sistemi Integrati. Due to the wide band-gap properties of this material, these devices are very well-suited for high-power applications, and must be characterized under strongly nonlinear and high-power conditions. An extensive power characterization of devices fabricated on GaN grown either on SiC or sapphire substrates is carried out, including pulsed I-V, power sweeps, and load-pull measurements in different bias conditions from class A to class B. An active load-pull bench optimized for high-voltage and high-power measurements allows the load-pull characterization to be extended to the whole Smith chart and the optimum loads to be localized, even for devices with almost reactive optimum terminations. The characterization procedure is performed on HEMT devices fabricated with different technologies and different layouts, in order to improve and refine the fabrication methodology and verify the scaling rules and the effects of defects and thermal degradation. SELEX SI devices show a growing maturity, with performances comparable to state-of-the-art technology.