Transparent TiN Electrodes in GaN Metal–Semiconductor–Metal Ultraviolet Photodetectors

GaN-based ultraviolet (UV) photodetectors were fabricated with transparent TiN electrodes. It was found that the transmittance was higher than 80% for a 50-nm-thick TiN layer. It was also found that we can significantly reduce the dark current of the photodetectors by inserting a thin Ba 0.25 Sr 0.75 TiO 3 (BST) interlayer between the TiN electrode and the n-GaN. With a 3-nm-thick BST interlayer, we can realize a TiN/BST/GaN photodetector with a photocurrent-to-dark current contrast as high as 2.5 × 10 4 .