It was previously reported that spectrally matched n-SiC and n-GaN-based MIS Schottky barrier diode structures exhibited optical emission and photosensitivity in the near-ultraviolet (UV) range of the spectrum and rectification at elevated temperatures. However, such structures were not practical due to the low mechanical and thermal stability of the semitransparent Au contacts. In addition, we experienced difficulties in achieving stable optical emission from the n-GaN-based structures. In this work various Schottky barrier diode structures based on p-type GaN layers grown on sapphire with silicon (Si), boron nitride (BN), and silicon dioxide (SiO2) interfacial layers were investigated. Blue and wide-spectrum optical emissions at forward and reverse bias, respectively, and photosensitivity were observed from these structures. A spectral match in the range of 365-400 nm between the light emitting diode (LED) and photodetector structures fabricated on the same substrate was achieved. A total Lambertian radiant UV power of similar to 466 muW was measured from a blue/UV LED at 22 V. UV-transparent and electrically conductive SnOx layers were fabricated, characterized, and employed for fabrication of p-GaN-based photodiode structures.