In this lab you will be using Light-Emitting Diodes (LEDs) as a source of photon
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Question
In this lab you will be using Light-Emitting Diodes (LEDs) as a source of photons. A diode is a semi-conductor device that usually only passes current in one direction, a very useful property in circuits. Semiconductors come in several varieties. In a diode there are two adjacent materials, one that has a slight excess of free electrons (known as "n-type", because it has more negative carriers), and one that has extra "holes" for electrons to go (known as "p-type", because it has a deficit of free electrons, and therefore has net positive carriers). [You can think of a "hole" like an empty spot on a crowded freeway- one car can move into it, but that leaves the gap somewhere else. A "hole" has a positive charge of 1.6 times 10^-19 Coulombs, just the opposite of an electron. Both electrons and holes can carry current.] In a diode with no voltage across it (as shown at right), there is a small region, known as the depletion layer, where the extra electrons of the n-type material leak over to "fill in" the holes of the p-type material. In this region there are essentially no free charge carriers, and therefore, no possibility to conduct a current through the diode. What happens when we put a voltage across the diode? Considering the diagrams below, circle your answer to what will happen to the thickness of the depletion layer for each orientation of the battery.Explanation / Answer
The first figure represent a situation called as "Reverse Biased " connection of Diode to the Source. In this situation, negative terminal of Battery is conncted towards "p" side and positive terminal of battery is connected to "n" side of Diode. Applied Electic Field by Battery acts in the depletion region from "n" side to "p" side, which will further block movement of free charge carriers, therefore Depletion region widens
The Second figure represent a situation called as "Forward Biased " connection of Diode to the Source. In this situation, negative terminal of Battery is conncted towards "n" side and positive terminal of battery is connected to "p" side of Diode. Applied Electic Field by Battery acts in the depletion region from "p" side to "n" side, which will further start movement of free charge carriers, therefore Depletion region thickness decreases
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