Probing the peculiar emission behaviors of c-Sapphire wafer and β-Ga2O3/c-Sapphire via hard X-ray nanoprobe

Sunny Saurabh^1*, Umeshwar Reddy Nallasani², Tzu-Chi Huang^3,1, Chun-Yen Lin², Yi-Chen Li¹, Yu-Hao Wu^4,1, Chien-Yu Lee¹, Bo-Yi Chen¹, Gung-Chian Yin¹, Mau-Tsu Tang¹, Wu-Ching Chou², Bi-Hsuan Lin¹

¹National Synchrotron Radiation Research Center, Hsinchu, Taiwan
²Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
³Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
⁴Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Sunny Saurabh, email:saurabh.s@nsrrc.org.tw

We report the intriguing phenomena of evolution of color centers (F and F+) using time-dependent X-ray excited optical luminescence (XEOL) in c-plane Sapphire wafer, β-Ga2O3/c-Sapphire and GaSe/β-Ga2O3/c-Sapphire. The increasing emission intensity of F+ and F-color centers over time indicates the formation of new color centers by continuous exposure to X-ray irradiation. These oxygen vacancy defect states remained even after having layer of epitaxial thin film of β-Ga2O3, and subsequent GaSe of sub µm thickness on top due to high penetration depth of X-ray. Interestingly, defect states of β-Ga2O3 decrease with time suggesting passivation of defect states induced by long term exposure to X-ray radiation. Also, we demonstrated the effect of long term X-ray irradiation using XEOL map, revealing spatial variation in defect state emission intensities. Time-resolved XEOL was used to measure dynamics of luminescence decay of F+ color center and defect state emission of Ga2O3. These results suggest that the enhancement in color center emission after hard X-ray irradiation could be of significant importance in the quest of solid-state single-photon sources.

Keywords: Hard X-ray, XEOL