Under CopyrightCwiklinski, MaciejMaciejCwiklinski2022-12-062022-12-062022978-3-8396-1867-7https://publica.fraunhofer.de/handle/publica/425713https://doi.org/10.24406/publica-33010.24406/publica-330Gallium nitride (GaN) high-electron-mobility transistor (HEMT) technology appears as an appealing candidate for supporting a variety of millimeter-wave (mm-wave) applications with its unique combination of simultaneous high-voltage and high-frequency operation. However, despite the rapid advance in GaN HEMT technology, the reported available gain of the devices is still limited at higher mm-wave frequencies in comparison to the competing high-speed semiconductor processes. This work investigates several approaches to enhance the performance of GaN-based circuits operating within the mm-wave spectrum. The main aim is to provide a set of design approaches and techniques to enable broadband operation of mm-wave GaN power amplifier monolithic microwave integrated circuits (MMICs), with a particular focus on frequencies close to and beyond the 100-GHz mark. In order to fulfill this goal, these approaches need to simultaneously target distinct design levels. Furthermore, implementing the concepts investigated in this work on circuit-level result in several MMICs providing state-of-the-art performance among GaN-based power amplifiers.engallium nitride (GaN)power amplifiermillimeter-wave monolithic microwave integrated circuit (MMIC)high-electron-mobility transistor (HEMT)DDC::600 Technik, Medizin, angewandte Wissenschaften::620 Ingenieurwissenschaften::621 Angewandte Physikdoctoral thesis