Development of a resonant microwave technique for characterization of the electronic properties of wide bandgap semiconductors used for RF application

Electronic properties of wide bandgap semiconductors (SiC and GaN), used for RF microwave/millimeter wave devices, are currently characterized at DC or low frequencies. We propose to develop a novel, non-destructive, non-contact microwave instrument andtechnique for the characterization of wide bandgap semiconductor substrates and epitaxial layers used in high frequency transistors and amplifiers. The goal of this project is to demonstrate the feasibility of resonant cavity microwave techniques (bothconfocal Fabry-Perot resonator and near field resonant cavity) for the electromagnetic characterization of SiC substrates and GaN epilayers. The proof-of principle measurements will be performed on an optimized and modified 94 GHz Fabry-Perot resonator.Experimental studies will be combined with 3D electromagnetic simulations to enable quantitative interpretation of the measured physical parameters. To understand the microwave properties of wide bandgap semiconductors and identify the important lossmechanisms, we will cross compare high frequency EM properties of the studied materials with their low frequency and DC electronic properties, and correlate them with the wafer growth/processing parameters. Near field cavity designs will be optimized bynumerical simulation. Phase I will result in a conceptual design of a non-contact microwave mapping test system in the X-band with a variable temperature platform (25 to 600¿C). Based on systematic studies of loss mechanisms in wide bandgap semiconductorsat microwave frequencies, we will provide a feedback from the wafer/epilayer evaluation to the material/device manufacturers, which will be used in the optimization of the wafer, epi and device production processes. Successful implementation of the resultsand data obtained in Phase I and Phase II will help to improve the quality, long-term stability and reproducibility of GaN/SiC-based devices. It will be beneficial for the development of advanced processing technologies and for the establishment of novelcharacterization principles for the wide bandgap semiconductors, aimed at high frequency device applications.As a result of the Phase II effort, a standard technique and a prototype instrument for non-contact rapid EM characterization of wide bandgap semiconductors in the microwave frequency range will be developed. This instrument will be useful for the highfrequency EM characterization of a wider range of materials.