In the solid state physics of semiconductors, carrier generation and recombination are processes by which mobile electrons and electron holes are created and eliminated. Electrons in the valence band cannot carry electrical current because they are immobilized by the electrons occupying the other valence band states. Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ... In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ...

In carrier generation, an electron in the valence band acquires energy from random interactions with other carriers, or with the lattice of the material, to be excited into the conduction band. This leaves an empty state in the valence band. This empty state, or electron hole, behaves as if it were itself a charged particle, and flows of holes form currents in the material. Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ... The ordinary meaning of lattice is the basis for several technical usages A cherry lattice pastry A mathematical lattice that is a type of partially ordered set. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ... In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. ...

Conversely, an electron in the conduction band and a hole in the valence band can recombine, resulting in the elimination of both charge carriers. In a material at thermal equilibrium generation and recombination are balanced, so that the net charge carrier density remains constant. The equilibrium carrier density that results from the balance of these interactions is predicted by thermodynamics. The resulting probability of occupation of energy states in each energy band is given by Fermi-Dirac statistics. In thermodynamics, a thermodynamic system is in thermodynamic equilibrium if its energy distribution equals a Maxwell-Boltzmann-distribution. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... Thermodynamics (from the Greek thermos meaning heat and dynamis meaning power) is a branch of physics that studies the effects of temperature on physical systems at the macroscopic scale. ... Fermi-Dirac statistics - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...

As the electron moves from one energy band to another, its gained or lost energy must take some other form, and the form of energy distinguishes various types of generation and recombination:

Schockley-Hall-Read (SHR)

The electron in transition between bands passes through a state created in the middle of the band gap by an impurity in the lattice. The impurity state can absorb differences in momentum between the carriers, and so this process is the dominant generation and recombination process in silicon and other indirect bandgap materials. The energy is exchanged in the form of lattice vibration, or phonon, exchanging thermal energy with the material.

photon exchange

During radiative recombination, a photon is emitted with the wavelength corresponding to the energy released. This effect is the basis of LEDs and semiconductor lasers. Because the photon carriers relatively little momentum, radiative recombination is significant only in direct bandgap materials. In the corresponding generation process, a photon is absorbed. This process is active in photodiodes, solar cells, and other semiconductor photodetectors

Auger recombination

The energy is given to a third carrier, which is excited to a higher energy level without moving to another energy band. After the interaction, the third carrier normally loses its excess energy to thermal vibrations. Since this process is a three-particle interaction, it is normally only significant in nonequilibrium conditions when the carrier density is very high. The Auger generation process is not easily produced, because the third particle would have to begin the process in the unstable high-energy state.