GaN Integrated Circuit Power Amplifiers: Developments and Prospects

GaN integrated circuit technologies have dramatically progressed over the recent years. The prominent feature of GaN high-electron mobility transistors (HEMTs), unparalleled output power densities, has created a paradigm shift in the established and emerging high-power applications. In this article, we present a review on the developments and prospects of GaN integrated circuit power amplifiers (PAs). The progress of GaN transistors including improvements in their important features, i.e., supply voltage, substrate material, transistor scaling approach, and device modeling are elaborated and the current state-of-the-art processes with 20-nm gate length, 450 GHz cut-off frequency, and over 600 V supply voltage are discussed. We also investigate developments in the GaN integrated circuit PA architectures and their implementation challenges including the reactive matching PAs capable of delivering over 100 W output power and operating up to 200 GHz, PA linearity, back-off efficiency enhancement, reconfigurable PAs, and distributed PA architectures. Finally, we discuss the prospects of GaN technology and possible future improvements, in transistor and circuit levels, which can advance performance and functionality of GaN integrated circuits.