1-Alex Kardomateas photodiodes

1-Alex Kardomateas photodiodes - Modes of Operation...

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Alex Kardomateas ECE 3080
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Basics ± Photodiodes are photodetectors capable of converting light to current or voltage ± They are most commonly used to measure light intensity ± Often use P-I-N junctions instead of P-N junctions because they are faster and more sensitive
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P-I-N Photodiodes ± A P-I-N junction is like a P-N junction but with a layer of intrinsic semiconductor seperating the p- type and n-type materials ± The intrinsic layer extends the width of the depletion region so more electron-hole pairs may be formed ± Surface layer is thin so that most optical absorption occurs in the intrinsic layer
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Operation ± An electron-hole pair is created when a photon strikes the diode with enough energy to excite the electron ± Because of the built-in field in the depletion region, electrons move toward the N region and holes move toward the P region creating a photocurrent
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Unformatted text preview: Modes of Operation Photovoltaic mode when no bias is applied to the diode, the flow of current is restricted and voltage builds up Photoconductive mode when a reverse bias is applied to the diode, depletion layer width increases and junction capacitance decreases Current-Voltage Characteristic Properties Dark current includes photocurrent from background radiation and saturation current of the junction Responsivity ratio of photocurrent to incident light power Materials Silicon low dark current, high speed, good sensitivity between 400-1000nm Germanium high dark current, slow speed, good sensitivity between 600-1800nm Indium Gallium Arsenide expensive, low dark current, high speed, good sensitivity between 800-1700nm...
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1-Alex Kardomateas photodiodes - Modes of Operation...

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