Enhanced Light Extraction and Electrical Properties in Ultraviolet-C AlGaN Light-Emitting Diodes with Porous Hole-Array Patterns

AlGaN-based ultraviolet-C (UVC) light sources have the potential to replace mercury lamps by improving the external quantum efficiency. High external quantum efficiency AlGaN UVC light-emitting diodes (LEDs) were demonstrated by forming hole-array patterns with a porous-AlGaN structure. The n-type AlGaN:Si layer at the hole-array pattern had been transformed into a porous-AlGaN structure through an electrochemical (EC) wet-etching process. The electroluminescence (EL) emission intensity of the UVC-LED with the EC-treated hole-array pattern was higher than that of the nontreated UVC-LEDs by forming a low effective refractive index and roughened porous-AlGaN surface layer. The peak EL wavelength blue-shift phenomenon and lattice constant that slightly reduced in the EC-treated AlGaN:Si layers were observed in the EC-treated UVC-LED structure, which was caused by the partial strain release in the AlGaN active layer. UVC-LED structures with an EC-treated hole-array pattern and porous sidewall structures have been demonstrated to improve light extraction efficiency and suppress the leakage current on plasma dry-etched sidewall structures. The n-type AlGaN:Si layer was wet-etched as the radiative pipe-shaped structure surrounding each hole pattern. Both the TE-mode and TM-mode EL far-field intensities were increased by adding a hole-array pattern with a porous-AlGaN structure. The AlGaN UVC-LED with an EC-treated porous hole-array structure has been demonstrated for high-efficiency UVC light source applications.