A photo-detecting device includes a first nitride layer, a light absorption layer disposed on the first nitride layer, and a Schottky junction layer disposed on the light absorption layer. According to a photoluminescence (PL) properties measurement of the photo-detecting device, a first peak light intensity is greater than a second peak light intensity, and the first peak light intensity is a peak light intensity of light emitted from the light absorption layer, and the second peak light intensity is a peak light intensity of light emitted from the first nitride layer.