Deep-UV Porous AlGaN Distributed Bragg Reflectors for Deep Ultraviolet Light-Emitting Diodes and Laser Diodes

A porous-Al0.47GaN/n-Al0.47GaN stack structure with a large refractive index contrast has been fabricated through a homoepitaxial growth process on a Si-doped n+-Al0.47GaN/n-Al0.47GaN stack structure with a simple electrochemical wet etching process. A 20-pairs porous-Al0.47GaN distributed Bragg reflector structure (DBR) with a high aluminum content was fabricated at the deep-ultraviolet wavelength region of light emitting diodes. Low compressive strain and high reflectance has been observed in a porous-AlGaN/n-AlGaN DBR structure with 93% reflectivity at 276 nm. The high reflectance spectrum was measured at the 265 to 287 nm wavelength region in the porous AlGaN DBR structure. The absorption wavelength of the AlGaN layer was observed at about 250 nm, which is shorter than the high reflectance wavelength region of the porous DBR. Light extraction efficiency of the deep-UV optoelectronic devices can be improved by integrating the embedded porous AlGaN reflectors during the epitaxial growth process.