It is based on the principle that the resistance of certain semiconductors materials decreases when they are exposed to radiations. In others words such material have high dark resistance and low irradiated resistance. … These charge carriers are created within the material and reduce its resistance.
What are photoconductive devices?
A photoconductive detector is also a semiconductor device made of two metallic contacts with diverse geometries deposited on a high-dark-resistivity semiconductor separated by a few micrometers, typically between 1 and 50 μm. Photoconductive switches are usually not biased when used as detectors.
What is photoconductive effect?
The photoconductive effect is the result of several processes whereby photons cause electrons to be ejected from the valence band and injected into the conduction band (Figure 1). The number of conduction electrons and holes increases simultaneously, and the effect is called intrinsic photoconductivity.
Where are Photoconductors used?
Because the current ceases when the light is removed, photoconductive materials form the basis of light-controlled electrical switches. These materials are also used to detect infrared radiation in military applications such as guiding missiles to heat-producing targets.
How is photoconductivity calculated?
Experimental Methodology
- Check the ohm law in the contacts in the dark.
- Measure the residual conductivity (residual or dark current Io)
- Measure the steady state photoconductivity for each wavelength.
- Measure the lamp signal for each wavelength, correct according to the detector response (using a rule of three)
What is negative photoconductivity?
In contrast to positive photoconductivity, negative photoconductivity (NPC) refers to a phenomenon that the conductivity decreases under illumination. It has novel application prospects in the field of optoelectronics, memory, and gas detection, etc.
What is photovoltaic detector?
(foh-toh-vol-tay -ik) An electronic device designed to detect photons of electromagnetic radiation. This type of instrument is used in astronomy to detect ultraviolet and infrared radiation; for example, an indium antimonide (InSb) detector is used in the near-infrared (see infrared detectors). …
What are photoconductors made of?
Intrinsic photoconductor materials include lead sulfide, lead selenide, cadmium sulfide, and mercury cadmium telluride, while germanium and silicon are the usual hosts for extrinsic photoconductors with impurities such as arsenic, copper, gold, and indium.
Which is used in photoconductive cell?
Cadmium sulfide (CdS) and cadmium selenide (CdSe) are the two materials normally used in photoconductive cell manufacture. Both respond rather slowly to changes in light intensity. … The spectral response of a cadmium sulfide cell is similar to that of the human eye; it responds to visible light.
Which of the following is photoconductive cell?
Explanation: Photoconductive cells are materials which changes conductivity on the application of light. Explanation: Photo junction diodes are semiconductor layers formed by silicon and germanium which are used in photovoltaic cells. 9. Which of the following are used to form photo transistors?
Is photoconductive cell a transducer?
Photo Electric Transducers: A photoelectric transducer can be categorized as photoemissive, photoconductive, or photovoltaic. In photoemissive devices, radiation falling on a cathode causes electrons to be emitted from the cathode surface.
Is quartz used in photoconductive cell?
(also photoresistive cell, photoresistor), a semiconductor device whose electrical conductivity or resistance changes upon exposure to optical radiation (see). The semiconductor is deposited as a thin film on a glass or quartz substrate or is cut as a thin wafer from a single crystal. …
How is responsivity calculated?
This value can be used to calculate the responsivity of the sensor by the following equation:
- = Photon Detection Efficiency.
- = Wavelength.
- = Gain.
- = Electron Charge.
- = Afterpulsing Probability.
- = Crosstalk Probability.
- = Planck Constant.
- = Speed of light.
What are the types of photodetectors?
Common Types of Photodetectors
- p-n Photodiodes. …
- p-i-n Photodiodes. …
- Avalanche Photodiodes. …
- MSM Photodetectors.
Which type of light will be detected by a photodiode?
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device.
What is photoconductivity response time?
The reported photoconductivity response time as measured from photocurrent decay ranged from a few tens of nanoseconds to a few minutes (Misra et al., 1995; Kung et al., 1995; Binet et al., 1996a).
How does a photoconductor work?
A photoconductor is of the former type: there are no conduction energy levels near the last one filled valence level so it is an insulator. But it becomes a conductor when exposed to light because the light can move the valence level electrons into empty conduction levels at much higher energies.
Is selenium A photoconductor?
A-Se is well developed technologically as it has been used as a photoconductor in photocopiers and also in an X-ray imaging technique known as xeroradiography for decades. It is used in its amorphous form, so amorphous selenium plates can be made by evaporation.
What is photoconductive transducer?
A device that is intended to change its conductance as a function of incident radiant flux.
What is photoconductivity in semiconductor?
Photoconductivity is the increase in electrical conductivity produced by shining light on a material. … This latter phenomenon is particularly pronounced in semiconductors when the band gap is small and light is able to excite electrons from the full valence band into the empty conduction band.
What is conductivity of a material?
Conductivity is the measure of the ease at which an electric charge or heat can pass through a material. A conductor is a material which gives very little resistance to the flow of an electric current or thermal energy. … Metals are the most conductive and insulators (ceramics, wood, plastics) the least conductive.
What is photoconductor and example?
Classic examples of photoconductive materials include the conductive polymer polyvinylcarbazole, used extensively in photocopying; lead sulfide, used in infrared detection applications, such as the U.S. Sidewinder and Russian Atoll heat-seeking missiles; and selenium, employed in early television and xerography.
Is light conductive?
A beam of light carries electric and magnetic fields, and as a result, energy and momentum, but it carries no electric *charge*. … The ions and electrons produced can then conduct electric current.