Multiscale Infrared Optical Characterizations of GaN: From Bulk Substrates to Fabricated Devices

Hossein Zandipour

Abstract: Gallium nitride (GaN) is reshaping the future of power and RF electronics, but unlike silicon, its material properties are still not nearly as well understood. In this talk, we will explore three complementary infrared optical studies of GaN materials and devices, moving from fundamental material behavior to prefabrication evaluation and finally to post-fabrication analysis. We first examine the temperature-dependent response of ammonothermal GaN substrates using Fourier Transform Infrared (FTIR) spectroscopy and dielectric function modeling, extracting carrier concentration and mobility across a range of thermal conditions. We then extend this approach to automated, spatially resolved FTIR mapping across a GaN substrate and generating two-dimensional maps of carrier concentration to assess doping uniformity prior to fabrication. Finally, we perform nanoscale near-field infrared imaging (s-SNOM) on a cross-sectioned GaN device to examine buried device interfaces.