01. Basics

Most metals have a positive temperature coefficient (PTC), which means that they conduct the better the colder they are.

Most semiconductors have a negative temperature coefficient (NTC), which means that they conduct the better the hotter they are.

So the coefficient is meant to be multiplied onto the resistance.

Energy Band Gap

The Energy Band Gap is the voltage zone where no charge "should" be.

conduction band
conduction band
conduction band
conduction band
conduction band
gap
gap
gap
gap
gap
gap
valence band
valence band
valence band
valence band

Silicium has an energy band gap of 1.1eV.

However, thermic work by the environment (if warm enough) on the element will suffice to elevate an electron from the crystal lattice (corresponding to the valence band) and make it move statistically through the element.

What remains is a hole, which also, by the thermic work by the environment, will move about statistically.

An electric field, as usual, will cause a drift movement across the element, holes in the direction of the field and electrons against the direction of the field.

Pair creation of electron/hole pairs and recombination will continue to happen in thermic equilibrium.

This natural pair creation (and recombination and pair creation and ...) will cause intrinsic conduction, which is useless, completely useless.

So the persistent search began on how to get Silicium to do something actually useful.

Found was that when you dope the element by a few foreign atom types with a different number of valence electrons, it will help things:

• You put an donator atom which has one electron too much together with the Silicium: A tiny amount of work, for Antimon: 0.04eV, will suffice to elevate the electron to the conduction band. Now you have a moveable electron, Negatively charged.
• You put an acceptor atom which has one electron too little together with the Silicium: To fill the need, an electron from the valence band can be taken, for the tiny amount of work, for Gallium: 0.04eV. Now you have a moveable hole, Positively charged.

N-type elements will have a LOT more free electrons than holes (holes just recombinate), so the majority carriers for N elements are the electrons. The minority carriers for N elements are the holes.

P-type elements will have a LOT more free holes than electrons (electrons just recombinate), so the majority carriers for P elements are the holes. The minority carriers for P elements are the electrons.

First Contact

If a P element and a N element are in contact, usually the majority carriers of one element will diffuse into the other element.

Depending on the electric field, that can change.

This is called a Diode.

Author: Danny (remove the ".nospam" to send)

Last modification on: Sat, 04 May 2024 in 01._Energy_Bands/index.php.