Wafer Level Integration of Self-Biased Ferrite Materials and Devices with Wide Band Gap Heterostructures

The circulator is historically an integral component of Defense and commercial phased array radar and communication systems. Unlike the vast majority of other components in the transmit and receive module (TRM), which have enjoyed the benefits of continued miniaturization and cost reduction, ferrite circulators have remained largely unchanged since their introduction. With future handheld mobile communication (i.e., 5G) technology proposed to operate at mm-wavelength, the development of two-dimensional full duplexing self-biased circulators having substantial weight and volumetric efficiencies would be required in heavily integrated, low cost mm-wave phased array communication systems and platforms. In this talk we will present the challenges and opportunities associated with hetero-epitaxial integration of hexagonal ferrite with common semiconductor platforms, such as Gallium Nitride (GaN) and Silicon Carbide (SiC). Issues of process compatibility, thermal diffusion, lattice and thermal expansion coefficient matching and deposition methods will be discussed for both high temperature (front-end) and low temperature (back-end) integration schemes. We will present the foundations of materials optimized for use in circulators and isolators. Emphasis will be placed upon the hexaferrite systems (i.e., magnetoplumbite structure) since they uniquely provide internal magnetic fields capable of both self-bias properties and high frequency (i.e., from Ka through W bands) performance.