Selective Detection of Blue and Ultraviolet Light by An InGaN/GaN Schottky Barrier Photodiode

Light in wavelength ranges of 400 and 350 nm was selectively detected by changing the bias voltage of the diode. Piezoelectric field in a 20-nm-thick InGaN layer on an n-GaN/sapphire structure in combination with a back-incidence configuration was successfully utilized. The principle is based on a fact that a strained InGaN layer has an inward electric field, whereas the n-type underlayer has an outward field. Using a circular Schottky electrode of 1 mm diameter surrounded by an ohmic electrode, a responsivity of 0.06 A/W was obtained for both wavelength ranges by choosing a bias of either 0 or -5 V.