How Do Majority and Minority Carriers Differ?

• Electrons are the majority, holes the minority (n-type)
• Holes are the majority, electrons the minority (p-type)

What you will learn

• Tell majority carriers from minority carriers.
• Say which kind is the majority in n-type and p-type material.
• Explain why minority carriers are scarce yet still matter.

Before you start

No prior knowledge is needed. You only need to remember that an electron is a negatively charged particle and a hole is a missing electron in the crystal.

What are majority and minority carriers?

The majority carrier is the more abundant kind and the minority carrier the less abundant. PVEducation's page on doping says that in doped material there is always more of one type of carrier than the other. The type with the higher concentration is called the majority carrier and the one with the lower concentration the minority carrier.

The idea only means something once the material has been tipped to one side. According to the same page, the balance of electrons and holes in a silicon crystal can be shifted by doping it with other atoms.

How does doping decide which side wins?

Doping uses atoms with one more or one fewer valence electron than silicon. Atoms with one more are used to make n-type material, so more electrons are added to the conduction band. Atoms with one fewer produce p-type material. The net result is a hole, because there are not enough electrons to form all the covalent bonds around the atoms.

• n-type doping: one extra electron
• p-type doping: one electron missing, forming a hole

Electronics Tutorials sums it up: in n-type material the majority carriers are electrons and the minority carriers are holes. In p-type material the majority carriers are holes and the minority carriers are electrons.

Where do minority carriers come from and why are there so few?

PVEducation says minority carriers are created either thermally or by incident photons. They are few because doping raises the majority, and the majority fills in part of the minority. The page on equilibrium carrier concentration says the number of majority carriers is approximately equal to the doping, and the number of minority carriers decreases as the doping level increases. One reason it gives: in n-type material some of the extra electrons fill holes in the valence band.

• Light doping: medium majority, minority still fairly tall
• Heavy doping: very tall majority, very short minority
• Higher doping level

The gap can be huge. In a typical semiconductor example on the doping page, the ratio of minority to majority carriers is less than one person to the entire population of the planet.

Why do minority carriers still matter?

Because they decide what happens after the material is disturbed. According to the page on minority-carrier lifetime, when minority carriers are raised above equilibrium by an external excitation, the excess decays back to the equilibrium concentration through recombination. Minority-carrier lifetime is the average time a carrier can spend in an excited state after electron-hole generation before it recombines.

• Light creates an electron and a hole
• They move toward each other
• Recombination: both vanish

Real-world example

Picture a comparison: a stadium full of fans in blue shirts with only a few in yellow. Blue is the majority and yellow the minority. If a group of yellow-shirted fans suddenly walks in, the count of yellow jumps compared with before, then falls as they leave one by one. This is only a comparison to help picture it, not an exact description of a semiconductor.

Common misunderstandings

Minority carriers are rare so they are useless. They are few, but after a disturbance it is they that decay back toward equilibrium through recombination.

N-type material contains only electrons. N-type material still contains holes, just very few. They are its minority carriers.

The majority carrier is always the electron. Only in n-type material. In p-type material the majority carrier is the hole.

Frequently asked questions

What is a majority carrier?

The kind of carrier with the higher concentration in doped material.

What is a minority carrier?

The kind of carrier with the lower concentration in doped material.

Which kind is the majority in n-type and p-type material?

N-type has electrons as the majority. P-type has holes as the majority.

How are minority carriers created?

Thermally or by incident photons.

Summary

• The majority carrier is the more abundant kind and the minority carrier the scarcer kind in doped material.
• N-type has electrons as the majority, p-type has holes as the majority.
• More doping means fewer minority carriers, yet they still govern how the material returns to equilibrium.