Photon detector is a solid-state electronic device made of semiconductor materials, mainly including photoconductive detector and photovoltaic detector.
Photovoltaic detectors are usually made of semiconductor PN structure. Its principle is to use the built-in electric field of PN junction to sweep the photogenerated carriers out of the junction region to form a signal. When the detector is exposed to light (irradiation) and intrinsic light absorption occurs in the body, two kinds of photogenerated carriers (electrons and holes) with opposite charges are generated. At first, these two photogenerated carriers are limited to the illumination region. Then, due to the concentration gradient, some of them diffuse to the PN junction region. Under the action of the built-in electric field in the PN junction, they gather at both ends of the junction to form a voltage signal. If both ends of the PN junction are connected into a loop, a current signal is formed.
Photon detector is a detection device with selective response wavelength. Only when the incident photon energy is greater than the electron activation energy E in the photosensitive material can the detector respond. For external photoelectric effect devices, such as phototubes and photomultiplier tubes, e is equal to the work to be done when electrons escape from the photocathode, which is generally slightly greater than 1 electron volt. Therefore, such detectors can only be used to detect near-infrared radiation or visible light. For photovoltaic detector and intrinsic photoconductive detector, e is equal to the band gap of semiconductor; For extrinsic photoconductive detectors, e is equal to the ionization energy of impurities. Because the two parameters of band gap width and impurity ionization energy have great choice, the response wavelength of semiconductor photonic detector can be adjusted in a wide range. For example, photoconductive detectors made of intrinsic germanium are sensitive to near-infrared radiation; The photoconductive detector made of impurity doped germanium can be sensitive to both mid infrared radiation (such as germanium mercury doped detector) and far infrared radiation (such as germanium gallium doped detector).
Difference between thermal detector and photon detector
The energy exchange process of the thermal detector includes thermal resistance effect, thermovolt effect (the reversibility of Peltier (% 1tier) effect), hot gas fan7530mx dynamic effect and pyroelectric effect. The energy conversion process of photon detector includes photovoltaic effect, photoconductivity effect, photoelectric magnetic effect and photoelectron emission effect (external photoelectric effect). A rough comparison of the two detectors is shown in table 3-9. Thermal resistance effect: when the temperature of the material changes, its conductivity will also change, which is the thermal resistance effect. Thermovolt effect: when heating the connection point of two different materials, a voltage will be generated at both ends of the open circuit, which is the thermovolt effect.
