Photodetector, photodiode

The photodiode is a semiconductor diode that functions as a photodetector. Photodiodes are packaged with either a window or optical fiber connection, in order to let in the fight to the sensitive part of the device. They may also be used without a window to detect vacuum UV or X-rays. 

Photometer, Table 2 Comparison of two photodetectors photodiodes and photomultipliers... 

Fig. 5. Device model for an MIS photodiode, the basic building block of the CCD photodetector. The depletion region is generated by the battery...

Photodetectors operate by carrier transport across a semiconductor junction. A wide variety of these photodiodes are available, such as Schottky diodes, phototransistors, and avalanche photodetectors. Typical photodetector materials are gallium arsenic phosphide and gallium phosphide, which are produced by MOCVD or MBE. 

A photodetector with a suitable spectral response for the detection of the fluorescence emission. As mentioned above, the fluorescence of most Cr3+-activated materials consists of either the red R-lines or a broadband infrared emission with the peak wavelengths ranging from -750 to 1000 nm, or both emissions. Thus, the widely available, compact and inexpensive silicon PIN photodiodes are the most suitable photodetectors for these applications. In some particular circumstances, where high speed and high sensitivity of detection are required, a silicon-based avalanche diode could be the best alternative to the PIN photodiode, at small price premium ... 

The developed prototype includes a source of ultraviolet (UV) radiation (1) with the wavelength of 350 nm, two photodiodes (2 and 3) based on a silicon monocrystal and placed at the angle of 20-25° relative to the plate with sNPS layer (4) and a photodiode (5) for detection of the incident UV light (Fig. 9.6). Upon adsorption of biomolecules the level of the sNPS photoluminescence and the output of the voltage of the consecutively connected photo detectors decrease. Use of two photodetectors of photoluminescence increases the biosensor sensitivity. 

When a semiconductor is bombarded with photons equal to or greater in energy than the band gap, an electron-hole pair is formed. The current that results is a direct function of the incident light intensity. Photoconductive devices consist of a p-n junction called a photodiode, or a p-i-n junction commonly used in a photodetector, an... 

There are other light detectors of interest in luminescence measurements such as photodiodes and other solid-state devices. Their sensitivity is very low compared with PM tubes, and there is a requirement for considerable amplification of the photocurrents. The solid-state photodetectors have the advantage of broad wavelength response in the IR region, beyond the range of PM tubes. 

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