Ultraviolet GaN Light-Emitting Diodes with Porous-AlGaN Reflectors.

A GaN/AlGaN ultraviolet light emitting diode (UV-LED) structure with a porous AlGaN reflector structure has been demonstrated. Inside the UV-LED, the n-AlGaN/undoped-AlGaN stack structure was transformed into a porous-AlGaN/undoped-AlGaN stack structure through a doping-selective electrochemical etching process. The reflectivity of the porous AlGaN reflector was 93% at 374 nm with a stop-bandwidth of 35 nm. In an angle-dependent reflectance measurement, the central wavelength of the porous AlGaN reflector had blueshift phenomenon by increasing light-incident angle from 10° to 50°. A cut-off wavelength was observed at 349 nm due to the material absorption of the porous-AlGaN/u-AlGaN stack structure. In the treated UV-LED structure, the photoluminescence emission wavelength was measured at 362 nm with a 106° divergent angle covered by the porous-AlGaN reflector. The light output power of the treated UV-LED structure was higher than that of the non-treated UV-LED structure due to the high light reflectance on the embedded porous AlGaN reflector.