Wed February 22, 2012 By: Dhruva

why does the width of the depletion layer increase in reverse bias and why does it decrease in forward bias?

Expert Reply
Wed February 22, 2012
In forward bias, the p-type is connected with the positive terminal and the n-type is connected with the negative terminal.With a battery connected this way, the holes in the P-type region and the electrons in the N-type region are pushed toward the junction. This reduces the width of the depletion zone. Reverse-bias usually refers to how a diode is used in a circuit. If a diode is reverse-biased, the voltage at the cathode is higher than that at the anode. Therefore, no current will flow until the diode breaks down. Connecting the P-type region to the negative terminal of the battery and the N-type region to the positive terminal corresponds to reverse bias. The connections are illustrated in the following diagram: Because the p-type material is now connected to the negative terminal of the power supply, the 'holes' in the P-type material are pulled away from the junction, causing the width of the depletion zone to increase.
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