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.

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p-n Junctions

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P n junctions

p-n Junctions

ECE 2204


P n junctions1

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.


Continuity of fermi energy

Continuity of Fermi Energy


I t 0 ma when va 0 v

IT = 0 mA when Va = 0 V

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

drift

e ee

e eeeee

diffusion

h hhhhh

h hh

diffusion

drift


Built in voltage

Built-In Voltage

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


Questions

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?


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