During the 19th century many experiments showed how electrical properties varied with material structures. But not until the 1930’s and 40’s did scientists start to see the rectification and amplification possibilities of semi conductor materials. Now millions of transistors reside on a computer processor and as many as 400 million transistors can be present on a thumbnail size integrated circuit chip.
The usual explanations of how semi conductors work involve moving charge carriers of negative electrons and positive holes. They are an extension of the idea that unlike charges attract whilst like charges repel. My explanations see all particles and thereby all particle structures as having energy desires. Structures desire the most energy efficient, stable state for their particles but they do not act in isolation and are influenced by changes in neighbor structures. Semi conductor technology is all about such energy desires and energy pressures for change.
Science explains how photon energies from sun particles will travel through space to earth; it explains how visible light photons from particles in a blade of grass will enable your eye and brain particles to collect and interpret its shape and colour. But for some reason it does not see photons of energy as passing across the relatively vast spaces between the particles of atoms and structures of atoms.
I view particles as energy machines; they move toward a photon source to absorb energy and move away from that source when their energy need is satisfied. Such a view explains why all particles vibrate and why they hold one another at a distance in structures. Particle structures like atoms and molecules will naturally bind to other structures but only if by combining they become more energy efficient.
In structures mobile electrons play the role of gathering and distributing photon energies to other particles. That role requires them to keep their distance from other electrons and they do so via energy exchanges. Their photon energy links to nuclear protons supply those protons and thereby neutrons with their energy desires. What we term a “hole” is a a sign that the energy desires of the nuclear particles could be better satisfied if an electron occupied that location. Photon streams to nuclear particles are trying to attract electron outputting photons into that location.
The outer electrons of structures are the least photon energy bound to them. Some are strongly held (electrical insulators) and others weakly held (good conductors). Photon energy pressures will try to dislodge them; they can be a push caused by an approaching electron or a pull provided by a photon stream to a “hole” in another structure, whose energy needs are not being efficiently met by its current electron numbers.
Outer valence electrons are also the means by which atom and molecule structures photon energy link to one another to make larger material structure. Semiconductor materials like silicon and germanium are themselves energy stable and not good conductors of electricity. However, by doping with other elements we can upset their stability and makes them into highly conductive materials that will allow outer electron movements (current flows) when external voltages are applied.
Voltage is usually provided by a two pole source that delivers a surplus of electrons at one pole and a deficit of electrons at the other pole. The surplus electrons put photon pressures on outer electrons to move. The deficit is in the form of locations (holes) that desire to be occupied by an electron. Each pole will act independently for a minuscule time producing its own local pressures and particle movements. If a circuit exists with low resistance to electron movements continuous current will flow.
A one amp current flow is equivalent to 6.25 billion, billion outer electrons passing through a cross section of a conductor every single second. That might sound a lot but it is a small number relative to the outer electrons in a tiny length of a conductor and most of these electrons progress along a conductor length at less than tortoise pace. What does switch our lights on instantly are the photon energy exchange between those electrons. They act at light speed and consequently any movement of electrons in an electric cable will rapidly set in motion electrons that are even miles away in that same cable. For historical reasons the movement of electrons is seen as a current flow in the opposite direction.
Some structures hold onto their outer electrons strongly, others like silver and copper easily part with their outer electrons. The photon energy pressure needed to displace an outer electron it carries with it. In most circumstances such energy is tiny relative to its inherent or mass energy. That or some of that carried energy is released as photon energy when it engages with another atomic particle structure. The copper cables taking energy to appliances mildly warm; nickel chromium elements in toasters output high numbers of infra-red heat photons; light bulbs output the higher photon energies of visible light.