Trap Behavior of the Optical Power Fluctuation in AlGaN-Based UV-C LEDs Degradation

The trap behavior of the optical power (OP) fluctuation in the degradation of deep ultraviolet light-emitting diodes (DUV-LEDs) is investigated in this work. The OP fluctuation under current stress is related to the combined action of acceptor activation, migration, and recombination. After stress, the changes observed in the admittance spectroscopy and deep-level transient spectroscopy measurements are due to a reduction in electron traps at
${E}_{c}$
–20 meV (
${E}_{{1}}$
) and increases in electron traps at
${E}_{c}$
–0.5 eV (
${E}_{{2}}$
), 0.68–0.79 eV (
${E}_{{3}}$
), and 0.95–1.2 eV (
${E}_{{4}}$
). The electron trap
${E}_{{1}}$
, located at the active region interface, has a prominent proportion in the apparent charge distribution profile and recombines with holes to restrict their entry into the quantum wells. The other traps contribute to an increase in the leakage current and nonradiative recombination. Reduction of the interface traps would weaken the hole transport shielding effect, but the hole injection augmentation would be wasted in the nonradiative recombination centers when defects are greatly generated in the active region during the long-term operation. Our study dissects the complex mechanisms in the electrical stress-induced degradation of DUV-LEDs and provides a constructive perspective on fabricating high-reliability AlGaN-based devices.