Intermediate Topic 149 of 1102 Bonding & Molecular Structure
Doping
Adding trace impurities to a semiconductor to create n-type or p-type conductivity.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
In-depth explanation of Doping
Doping is the deliberate addition of trace amounts of an impurity to a semiconductor in order to change its conductivity dramatically. Adding a group 15 element such as phosphorus to silicon introduces extra valence electrons that are easily donated, creating n-type material in which electrons are the main carriers. Adding a group 13 element such as boron creates holes, giving p-type material. Only parts per million of dopant are needed to produce large changes in conductivity. Joining n-type and p-type regions forms a p-n junction, the basis of diodes, transistors and solar cells.
Going deeper: Doping
Key ideas: For silicon (group 14, four valence electrons) use group 15 donors (P, As) for n-type, and group 13 acceptors (B, Ga) for p-type. Typical doping levels are one atom per million to billion host atoms. The overall crystal remains electrically neutral, since the dopant nuclei carry compensating charge. A p-n junction forms a depletion layer that allows current in only one direction.
Common mistakes and connections: A major misconception is that n-type material is negatively charged and p-type positively charged, but both are neutral overall. Another is mistaking which group gives which type. Heavy doping makes the material behave nearly like a metal. Links to band theory, diodes, solar cells and LEDs.
Visualization of Doping
A phosphorus donor level lies only 0.045 eV below the conduction band of silicon, so room-temperature heat easily promotes its extra electron to conduct. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Phosphorus-doped silicon is n-type, because each phosphorus atom contributes an extra electron to the lattice.
Frequently asked questions about Doping
What is Doping?
Adding trace impurities to a semiconductor to create n-type or p-type conductivity.
Is Doping a beginner, intermediate or advanced topic?
Doping is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
What should I learn before Doping?
Study these earlier topics in Bonding & Molecular Structure first: Properties of Metals, Band Theory, Semiconductors.
What comes after Doping?
The next topics in Bonding & Molecular Structure are VSEPR Theory and Electron Domain Geometry.
Can I practise Doping with quizzes?
Yes. The interactive lesson includes a self-check question on Doping, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where Doping fits in Bonding & Molecular Structure
Doping is topic 34 of 104 in Bonding & Molecular Structure.