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The carrier particles, namely the holes and electrons of a semiconductor, move from a place of higher concentration to a place of lower concentration. Hence, due to the flow of holes and electrons there is a current. This current is called the diffusion current. The drift current and the diffusion current make up the total current in the conductor.
When an electron leaves a helium atom, it leaves an electron hole in its place. This causes the helium atom to become positively charged. 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.
Electron and hole trapping in the Shockley-Read-Hall model. In the SRH model, four things can happen involving trap levels: [11] An electron in the conduction band can be trapped in an intragap state. An electron can be emitted into the conduction band from a trap level. A hole in the valence band can be captured by a trap.
Electron and hole mobility are special cases of electrical mobility of charged particles in a fluid under an applied electric field. When an electric field E is applied across a piece of material, the electrons respond by moving with an average velocity called the drift velocity , v d {\displaystyle v_{d}} .
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 electric current.
In electronics, other forms of electric current include the flow of electrons through resistors or through the vacuum in a vacuum tube, the flow of ions inside a battery, and the flow of holes within metals and semiconductors. A biological example of current is the flow of ions in neurons and nerves, responsible for both thought and sensory ...
The current which will flow in an intrinsic semiconductor consists of both electron and hole current. That is, the electrons which have been freed from their lattice positions into the conduction band can move through the material. In addition, other electrons can hop between lattice positions to fill the vacancies left by the freed electrons.
Drift current density due to the charge carriers such as free electrons and holes is the current passing through a square centimeter area perpendicular to the direction of flow. (i) Drift current density , due to free electrons is given by: = (ii) Drift current density , due to holes is given by: = Where: