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# p-n Junctions PowerPoint PPT Presentation

p-n Junctions. ECE 2204. p-n junctions. When the same semiconductor is used to make the p-type region as the n-type region, the combination is called a homojunction . When two different semiconductors are used to make the p-n junction, it is called a heterojunction.

p-n Junctions

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## p-n Junctions

ECE 2204

### p-n junctions

When the same semiconductor is used to make the p-type region as the n-type region, the combination is called a homojunction.

When two different semiconductors are used to make the p-n junction, it is called a heterojunction.

### IT = 0 mA when Va = 0 V

• There are, however, carriers flowing constantly across the p-n junction.

drift

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diffusion

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diffusion

drift

### Built-In Voltage

• The built-in voltage is the voltage drop associated with the induced electric field between the p and n regions.

### Questions

• How does the built-in voltage change with increasing temperature?

• Compare the built-in voltage for

• p-n junction (Na = 1018 cm-3, Nd = 1015 cm-3)

• p-n junction (Na = 1015 cm-3, Nd = 1018 cm-3)

• p-n junction (Na = 1017 cm-3, Nd = 1016 cm-3)

• For the same doping concentration, which semiconductor, Ge or Si, does the p-n junction has the smaller built-in voltage?