Definition and Properties of Electron Holes
– Electron holes are quasiparticles denoting the lack of an electron at a position in an atom or atomic lattice.
– The absence of an electron leaves a net positive charge at the hole’s location.
– Holes in a metal or semiconductor lattice can move through the lattice and act similarly to positively-charged particles.
– Holes play a crucial role in the operation of semiconductor devices like transistors, diodes, and integrated circuits.
– Holes are different from positrons, which are the antiparticles of electrons.
Electron Holes in Solid-State Physics
– In solid-state physics, an electron hole is the absence of an electron from a full valence band.
– Holes help conceptualize the interactions of electrons within a nearly full valence band of a crystal lattice.
– The behavior of a hole in a semiconductor crystal lattice is comparable to the movement of a bubble in a full bottle of water.
– The concept of an electron hole in solid-state physics predates the concept of a hole in Dirac equation.
– Rudolf Peierls pioneered the hole concept in solid-state physics in 1929.
Simplified Analogy: Empty Seat in an Auditorium
– Holes in a crystal lattice can move to different positions by the motion of surrounding electrons, similar to an empty seat in an auditorium.
– Hole conduction in a valence band can be explained by imagining people moving along a row of seats in an auditorium.
– The empty seat moves closer to the edge as people in the crowded row move into it.
– If a hole associates itself with a neutral atom, that atom loses an electron and becomes positive.
– The hole is considered a single equivalent imaginary particle with a positive charge of +e, opposite to the electron charge.
Detailed Picture: A Hole is the Absence of a Negative-Mass Electron
– The dispersion relation determines how electrons respond to forces in a band, based on their wavevector and energy.
– Near the bottom of the conduction band, electrons have a positive effective mass and respond to forces as if they had the real electron mass.
– Electrons near the top of the valence band behave as if they have negative effective mass.
– The shape of the valence band causes electrons near the top to move in the opposite direction of a force.
– Positively-charged holes are used as a shortcut for calculating the total current of an almost-full band.
Applications of Electron Holes
– Electron holes are crucial for understanding and designing semiconductor devices like transistors, diodes, and integrated circuits.
– They play a significant role in phenomena like the Hall effect and Seebeck effect.
– Auger electron spectroscopy and computational chemistry utilize the concept of holes.
– Holes help explain the low electron-electron scattering rate in crystals.
– Understanding holes is essential for studying the electronic band structure of crystals. Source: https://en.wikipedia.org/wiki/Electron_hole
In physics, chemistry, and electronic engineering, an electron hole (often simply called a hole) is a quasiparticle denoting the lack of an electron at a position where one could exist in an atom or atomic lattice. Since in a normal atom or crystal lattice the negative charge of the electrons is balanced by the positive charge of the atomic nuclei, the absence of an electron leaves a net positive charge at the hole's location.
Holes in a metal or semiconductor crystal lattice can move through the lattice as electrons can, and act similarly to positively-charged particles. They play an important role in the operation of semiconductor devices such as transistors, diodes (including light-emitting diodes) and integrated circuits. If an electron is excited into a higher state it leaves a hole in its old state. This meaning is used in Auger electron spectroscopy (and other x-ray techniques), in computational chemistry, and to explain the low electron-electron scattering-rate in crystals (metals and semiconductors). Although they act like elementary particles, holes are rather quasiparticles; they are different from the positron, which is the antiparticle of the electron. (See also Dirac sea.)
In crystals, electronic band structure calculations lead to an effective mass for the electrons that is typically negative at the top of a band. The negative mass is an unintuitive concept, and in these situations, a more familiar picture is found by considering a positive charge with a positive mass.
