Data is reported on study of light-current characteristics and thermal properties of flip-chip AlGaN UV-C LED over a wide range of excitation levels: up to 2 kA/cm2 in pulse mode. The tailor-made microscope based on InAs matrix with  photosensitivity in 2.5–3.1 µm range was employed for getting IR-intensity maps and revealing of temperature distribution across the emitting chips. The work is aimed at detailed study the factors limiting the energy capabilities  of UV-C LEDs.