Gallium nitride high-electron-mobility transistors (GaN HEMTs) are at a point of rapid growth in defense (radar, SATCOM) and commercial (5G and beyond) industries. This thesis explores the aluminum nitride (AlN) platform as a candidate for future high-power, millimeter-wave (mm-wave) power am- plifiers. The AlN platform allows for optimized, highly-scaled heterostructure design with the potential for improved output power and thermal management of III-nitride amplifiers.The thesis begins with an overview of the GaN amplifier landscape, before focusing on the AlN/GaN/AlN heterostructure, laying out its advantages over the conventional and state-of-the-art GaN HEMT heterostructures. A robust large signal model, based on the Angelov model, is demonstrated and verified over the gigahertz frequencies. AlN/GaN/AlN HEMT results are explored, beginning with the measured breakdown characteristics before moving to the large signal performance of the HEMT at mm-wave frequencies. Development of and motivation for regrown ohmic contacts, T-gate contacts, and silicon ni- tride passivation are also covered. In addition to the n-channel amplifier, the progress of state-of-the-art high- current p-channel FETs, mature AlN bulk acoustic wave (BAW) filter technol- ogy, and advanced substrate-integrated waveguides (SIW), are discussed. The integration of all these components on a unifying AlN platform will unlock unprecedented integration in the III-nitride regime, with the potential for a new wave of innovation in mm-wave communication and high-power logic applica- tions.