The present disclosure relates to semiconductor structures and, more particularly, to photodetectors used with a broadband signal and methods of manufacture. The structure includes: a first photodetector; a second photodetector adjacent to the first photodetector; a first airgap of a first size under the first photodetector structured to detect a first wavelength of light; and a second airgap of a second size under the second photodetector structured to detect a second wavelength of light.