Question

The size of depletion layer is small.why

Answer 1

In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile charge carriers have been diffused away, or have been forced away by an electric field. The only elements left in the depletion region are ionized donor or acceptor impurities.

The depletion region is so named because it is formed from a conducting region by removal of all free charge carriers, leaving none to carry a current. Understanding the depletion region is key to explaining modern semiconductor electronics: diodes, bipolar junction transistors, field-effect transistors, and variable capacitance diodes all rely on depletion region phenomena.

The following discussion is limited to the p–n junction and the MOS capacitor, but depletion regions arise in all the devices mentioned above.

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Answer 2

Because Depletion region is a region near the p-n junction where flow of charge carriers is reduced over a given period and finally results in zero charge carriers. The width of depletion region is depends on the amount of impurities added to the semiconductor.

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