ABSTRACT
In this chapter, the authors discuss detector principles, system and wavelength considerations, detector structures, and high-speed operation and give selected experimental results. The heating caused by the absorbed energy is used in bolometers for mid- and far-infrared detectors where the low photon energy requires cooling of small-band gap semiconductors in photon detectors. In a semiconductor system otherwise photocurrent generation in photodiodes/phototransistors is the preferred method for light detection. A photoconductive device realizes the simplest photodetector. It exploits the change in conductivity of a semiconductor that is illuminated. The intrinsic photoconductivity involves the excitation of electrons and holes from a photon absorption process. The key mechanism of all photocurrent-based detectors is the separation of carriers by the electric field of a depletion layer. Si-based photonics benefits strongly from the mature technology and precision of fine structure lithography. This allows rapid progress in lateral incidence waveguide photodetectors because of fabrication of small-area photodetectors with high responsivity and high speed.
