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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