Metal-insulator-semiconductor Schottky barrier structures on GaN and 6H-SiC using highly stable interfacial BN layers have been investigated. As reported earlier, such structures fabricated with Ti contacts are capable of withstanding up to 350 and 600 degrees C when based on 6H-SiC and GaN, respectively. In this work we fabricated diode structures using interfacial BN layers and optically transparent Au contacts. Visible-blind photosensitive structures on GaN and 6H-SiC and prebreakdown light-emitting diode (LED) structures on 6H-SiC have been characterized. The radiant and spectral sensitivities of the photosensitive structures were measured in the range of 200-400 nm. The potential barrier heights determined from photoresponse measurements were 2.7 and 2.88 eV for GaN- and SiC-based samples, respectively. The spectrum of 6H-SiC and p-GaN-based prebreakdown LED structures measured through transparent Au electrodes extended to the ultraviolet region. The optical emission power of the 6H-SiC-based LED structures measured in the range 200-1100 nm saturated to about 10(-8) W at current densities close to 200 A/cm(2). Prospects for applications of the diode structures described in advanced visible-blind optoelectronic sensors are discussed.