Gallium nitride-based monolithic microwave integrated circuits (MMICs) can comprise aluminum-based metals. Electrical contacts for gates, sources, and drains of transistors can include aluminum-containing metallic materials. Additionally, connectors, inductors, and interconnect devices can also comprise aluminum-based metals. The gallium-based MMICs can be manufactured in complementary metal oxide semiconductor (CMOS) facilities with equipment that produces silicon-based semiconductor devices.