Intrinsic Semiconductors and Charge Carriers
Pure semiconductor behavior
Intrinsic means pure
An intrinsic semiconductor is a pure semiconductor with no intentional impurities added. In such a material, electrical current is carried by two types of mobile charge carriers: electrons and holes.
What is a hole?
A hole is not a physical particle, but a useful way to describe the absence of an electron in a bond. When an electron leaves its place, the missing spot behaves like a positive charge carrier.
Electron-hole pairs
When heat or light excites an electron into the conduction band, it leaves behind a hole in the valence band.
Current in a semiconductor
Current arises because electrons move one way while holes appear to move the opposite way. Both contribute to conduction, and both are important in semiconductor devices.
In a semiconductor, a hole is best described as:
A hole is a convenient way to describe the absence of an electron in a bond.
Correct answer: A missing electron that behaves like a positive charge carrier
Name the two main charge carriers in an intrinsic semiconductor.
Both electrons and holes help carry current.
Correct answer: electrons and holes
How intrinsic conduction happens
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Step 1: Start with a pure semiconductor crystal.
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Step 2: Give some electrons enough energy to leave bonds.
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Step 3: Electrons move in the conduction band.
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Step 4: The missing spots in bonds act like holes.
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Step 5: Both carriers contribute to current.
Why is an intrinsic semiconductor usually less conductive than a doped semiconductor?
Pure semiconductors have fewer free carriers than doped ones.
Correct answer: Because it has very few charge carriers available