What is Charge carriers: Definition and 22 Discussions

In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes. The term is used most commonly in solid state physics. In a conducting medium, an electric field can exert force on these free particles, causing a net motion of the particles through the medium; this is what constitutes an electric current. In conducting media, particles serve to carry charge:

In many metals, the charge carriers are electrons. One or two of the valence electrons from each atom are able to move about freely within the crystal structure of the metal. The free electrons are referred to as conduction electrons, and the cloud of free electrons is called a Fermi gas. Many metals have electron and hole bands. In some, the majority carriers are holes.
In electrolytes, such as salt water, the charge carriers are ions, which are atoms or molecules that have gained or lost electrons so they are electrically charged. Atoms that have gained electrons so they are negatively charged are called anions, atoms that have lost electrons so they are positively charged are called cations. Cations and anions of the dissociated liquid also serve as charge carriers in melted ionic solids (see e.g. the Hall–Héroult process for an example of electrolysis of a melted ionic solid). Proton conductors are electrolytic conductors employing positive hydrogen ions as carriers.
In a plasma, an electrically charged gas which is found in electric arcs through air, neon signs, and the sun and stars, the electrons and cations of ionized gas act as charge carriers.
In a vacuum, free electrons can act as charge carriers. In the electronic component known as the vacuum tube (also called valve), the mobile electron cloud is generated by a heated metal cathode, by a process called thermionic emission. When an electric field is applied strong enough to draw the electrons into a beam, this may be referred to as a cathode ray, and is the basis of the cathode ray tube display widely used in televisions and computer monitors until the 2000s.
In semiconductors, which are the materials used to make electronic components like transistors and integrated circuits, two types of charge carrier are possible. In p-type semiconductors, "effective particles" known as electron holes with positive charge move through the crystal lattice, producing an electrical current. The "holes" are, in effect, electron vacancies in the valence-band electron population of the semiconductor and are treated as charge carriers because they are mobile, moving from atom site to atom site. In n-type semiconductors, electrons in the conduction band move through the crystal, resulting in an electrical current.In some conductors, such as ionic solutions and plasmas, positive and negative charge carriers coexist, so in these cases an electric current consists of the two types of carrier moving in opposite directions. In other conductors, such as metals, there are only charge carriers of one polarity, so an electric current in them simply consists of charge carriers moving in one direction.

View More On Wikipedia.org
  1. A

    A The main charge carrier in the ionic crystal is polaron or conduction?

    Suppose I have a perfect crystal(e.g.TiO2-Rutile, band gap=3ev), under UV light, there should photoconductivity, according to the condensed matter theory, some of these excited conduction band electrons would form small polarons, I am wondering how many percent of the free conduction band...
  2. cemtu

    What makes up a "current" in solid state physics?

    If there is some incoming light that has hit electrons of a N-type doped silicon and broke loose these electrons from their covalent bounds and excited them to the conduction band and also excited the electrons in the donor energy level to the conduction band as well, here we know that, the...
  3. C

    How are holes charge carriers?

    Homework Statement:: Hi, It's been a while since I have reviewed my basic semiconductor physics and I have some doubts. In a P-Type doped semidoncutor material, I understand that Group III elements such as Boron are added to a Group IV element such as Silicon and thus the Boron atom has one...
  4. T

    In electrostatics, what is meant by positive charges?

    I am needing clarification for a concept. I understand that electrons carry a negative charge and that protons carry a positive charge. I also understand that a plastic rod picks up electrons when I rub it with a piece of wool. From the conservation of charge, the piece of wool must have a...
  5. S

    B Understanding Energy and Charge: Exploring the Basics

    I have a simple two-part question, or two simple questions. 1. What is energy? 2. What is charge? The charge I'm referring to is the charge on charged subatomic particles. And atom's charge is defined by the number of electrons and protons present in it. But an electron itself is called a...
  6. T

    Charge Carriers in the Hall Effect

    For a lab I just finished this past week, we were working with the hall effect and finding hall voltages. The metals used were p-germanium and n-germanium semi-conductors. I understand why in n-germanium the hall voltage is positive and p-germanium is negative assuming negative charge carriers...
  7. MathematicalPhysicist

    How Does Electron and Hole Density Change Over Time in Doped Semiconductors?

    Homework Statement You dope an $n$-type substrate at time ##t=0## with electrons and holes around the points: ##\vec{r}_{0,c}## and ##\vec{r}_{0,v}## respectively. The initial densities' distributions are: $$\Delta n (\vec{r},t=0) = \frac{\Delta N_0}{(2\pi...
  8. K

    I Minority charge carriers - what are these?

    Hi all, this question comes from an old related thread .. https://www.physicsforums.com/threads/help-in-semiconductors-minority-and-majority-carriers.613598/ I'm also interested in the definition of these 'minority charge carriers' in semiconductors. I don't understand the explanations in the...
  9. C

    How Many Electrons Does a Cathode Ray Tube Emit Per Second?

    Homework Statement The beam of electrons in a cathode ray tube contains electrons traveling at 8.4x106 ms-1 and the current throgh the tube is 2.8 micro A. a) how many electrons are emitted per second from the cathode of the tube b) what is the number of electrons per unit length of the beam...
  10. moenste

    Find drift velocity of the current carriers in the copper strip

    Homework Statement ABCD is a plane rectangular strip of conducting material of uniform thickness, with a steady current flowing uniformly from AD to BC. The potential difference between E and F, the mid-points respectively of AB and CD, is zero, but when a magnetic field is set up at right...
  11. AnonymousPT

    Field Effect Transistor - Minority Charge Carriers

    Unlike BJT, Why the minority charge carriers in FET do not participate in conduction? What is actually happening with the minority charge carriers?
  12. F

    Holes as positive charge carriers in semiconductors

    Hello Forum, An electric current is the flow of electric charge: charge in motion. The charges can be electrons, ions, etc. movingi in a solid, liquid, gas. When dealing with semiconductors the concept of hole is introduced. I understand that only the electrons are moving and the constitute...
  13. L

    What happens to the minor charge carriers in p-n junction diode

    what happens to the minor charge carriers in p-n junction diode when forward biased?
  14. S

    Do charge carriers affect the total charge of a material in solid state physics?

    In solid state physics the "holes" usually regarded as an effective positive charge carriers. In order to have neutral charge some object needs to have an equal amount of protons and electrons. If some material such as an intrinsic semiconductor has equal amount of protons and electrons + some...
  15. E

    Semiconductors, number density of charge carriers.

    Homework Statement It's the third part which I'm stuck on. Homework Equations The Attempt at a Solution I've substituted in all the numbers and, multiplied by the density but I am still not getting the correct answer; where a I going wrong? I got 6.13*(10^11) m^-3 The answer given is...
  16. I

    Why do charge carriers reside on the shell of a conductor?

    can someone please provide me with a proof or even just an intuitive explanation
  17. T

    Relationship between charge carriers per unit volume and resistance

    Why is the number of charge carriers per unit volume is inversely proportional to resistance?If there is more charges carrier, it doesn't increase the collision between free electron which causes in increase of resistance?sorry for my unclear concept of Electricity circuit.I hope there will be...
  18. L

    Positive and neagtive charge carriers current

    What would happen hypothetically if there was a positive charged particle the same size as an electron (that wasn't antimatter), that carried current in the opposite direction in a wire to a normal conventional current in another wire? According to the Lorentz force they would attract so again...
  19. E

    What happens to the speed of charge carriers when going through a resistor

    Hi everyone, I hope this question hasn't be asked and answered already in this forum, I searched through all related threads but I couldn't find an answer specific enough to my question. Consider a simple circuit with a DC battery and resistor. When the electrons (the charge carriers in...
  20. M

    Two charge carriers in the Drude model

    I'm studying Solid State Physics and I have some problems with a problem. It is stated like this: Consider a system of two charge carriers in the Drude model. The two carriers have the same density n and opposite charge (e and-e), and their masses and relaxation times are m1,m2 and r1,r2...
  21. K

    Charging by induction - Electrons the ONLY mobile charge carriers?

    Hi, This is my virgin post. This forum has been a great source of information for the past one year. I am a high school teacher from Singapore. In the study of electrostatics (more specifically induction), we often encounter the scenario below: Two insulated metal spheres touching...
  22. K

    Charge carriers per atom in graphene

    Hello. I'm trying to find the individual contributions of carbon atoms to the charge carriers in graphene. In other words, I'm trying to answer "How many charge carriers does one carbon atom supply?" Here is what I've done so far: Taking the max. carrier density as 10^13 1/cm^2 and the...