Substrate effects on GaN photoconductive detector performance

GaN photoconductive detectors were fabricated on three substrates: sapphire, SiC, and GaN-on-sapphire substrates. The undoped GaN was deposited on each substrate by metalorganic vapor phase epitaxy. The structural properties, as measured by transmission electron microscopy, x-ray diffraction, and atomic force microscopy, of the layers grown on GaN-on-sapphire and SiC were superior to those of the layers grown on sapphire. A corresponding improvement in optical response and sharpness of optical response of the photoconductive detectors was observed with improved material quality.