Deep-Ultraviolet Transient Grating Probes of Wide Bandgap Materials in a Reflective Heterodyne Geometry

Wide-bandgap materials offer promising thermal and electronic properties for next-generation electronic and photonic devices; however, they are transparent to visible light, and thus require new approaches to characterization [1,2]. Transient grating excitation using interfering laser beams has proven widely applicable to characterizing the thermal, acoustic, and electronic properties of semiconductors at length scales above ~1 um. Here, we present a tabletop deep-ultraviolet (DUV) transient grating (TG) system employing heterodyne detection to directly probe nanoscale transport dynamics in ultrawide bandgap materials such as diamond. Since visible TG is limited to greater than 1 µm periods, 200 nm deep-ultraviolet light is required to study non-diffusive behavior. A previous experiment used lenses to create TG excitations down to 287nm but this geometry did not allow for heterodyne detection [3]. By switching to an all-reflective geometry, we are able to take advantage of the high sensitivity of heterodyne detection to greatly boost signal to noise and separate the contributions of phonons, electrons and coherent acoustic oscillations which was previously only possible at visible wavelengths [4].



[1] Warzoha at al., Journal of Electronic Packaging 143, 020804 (2021)

[2] Tsao et al., Adv. Electron. Mater. 4, 1600501 (2018)

[3] E. E. Nelson et al, Phys. Rev. Applied 22, 054007 (2024)

[4] J. A. Johnson et al., Journal of Applied Physics 111 (2012)