BeginnerTopic 2 of 104Electronics & Embedded
Intrinsic and extrinsic semiconductors
Doping pure silicon with donors or acceptors creates n-type or p-type material.
In depth
Pure silicon is intrinsic with equal electrons and holes. Doping with group V atoms (phosphorus) adds free electrons (n-type); group III atoms (boron) add holes (p-type). Doping levels of 10¹⁵–10¹⁹ cm⁻³ control conductivity over many orders of magnitude.
Key points
- Majority and minority carriers
- Mass-action law n·p=nᵢ²
- Conductivity rises with doping
ExampleA resistor on a chip is a doped silicon strip.
Pure silicon conducts poorly, so adding tiny amounts of other atoms, a process called doping, is what makes it useful in circuits.
What is Intrinsic and extrinsic semiconductors?
Doping pure silicon with donors or acceptors creates n-type or p-type material.
Why is it important to understand intrinsic and extrinsic semiconductors?
Pure silicon conducts poorly, so adding tiny amounts of other atoms, a process called doping, is what makes it useful in circuits.
What is the difference between n-type and p-type?
N-type material has extra electrons from donor atoms such as phosphorus. P-type has holes from acceptor atoms such as boron.
Why does doping change conductivity so much?
A tiny fraction of dopant atoms adds many more carriers than the intrinsic material, so conductivity changes by orders of magnitude.
How is Intrinsic and extrinsic semiconductors used in practice?
Typical applications include making an n-type layer for the source of an NMOS transistor, forming a p-type region in a solar cell and adjusting the threshold voltage of a transistor during fabrication.
What should I learn before Intrinsic and extrinsic semiconductors?
Study "Atoms and energy bands" first (topic 1 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
What are the key points of Intrinsic and extrinsic semiconductors?
Majority and minority carriers. Mass-action law n·p=nᵢ². Conductivity rises with doping.
Can you give an example of Intrinsic and extrinsic semiconductors?
A resistor on a chip is a doped silicon strip.
What comes after Intrinsic and extrinsic semiconductors?
The next topic is "PN junction", which builds directly on this one.
How difficult is Intrinsic and extrinsic semiconductors?
It is classed as Beginner in Electronics & Embedded (topic 2 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.