As semiconductors have evolved and become more powerful, they have propelled many industries forward into a technological age. They are still an expensive component in many devices, so their pricing and demand trends go a long way in determining the profit potential of companies that sell devices with semiconductors in them. Chips are made by the billions each year, and their sales & pricing trends are widely followed by analysts as a harbinger of technology-related profits.
Semiconductor makers often see “boom and bust” cycles based on the underlying demand for chip-based products. When times are good profit margins can run very high for chipmakers; when demand falls through however, chip prices can fall dramatically and have a major affect on many industries’ supply chains.
Semiconductors have had a monumental impact on our society. You find semiconductors at the heart of microprocessor chips as well as transistors. Anything that’s computerized or uses radio waves depends on semiconductors.
A diode is the simplest possible semiconductor device, and is therefore an excellent beginning point if you want to understand how semiconductors work.
In this article, you’ll learn what a semiconductor is, how doping works and how a diode can be created using semiconductors. But first, let’s take a close look at silicon.
Silicon is a very common element – for example, it is the main element in sand and quartz. If you look “silicon” up in the periodic table, you will find that it sits next to aluminum, below carbon and above germanium.
Metals tend to be good conductors of electricity because they usually have “free electrons” that can move easily between atoms, and electricity involves the flow of electrons. While silicon crystals look metallic, they are not, in fact, metals. All of the outer electrons in a silicon crystal are involved in perfect covalent bonds, so they can’t move around. A pure silicon crystal is nearly an insulator-very little electricity will flow through it.
Semiconductor
The materials in which the electrical conductivity lies between conductors and insulators are called semiconductors. They have resistivity value between 10-14 ohm m to 0.5 ohm m .
The electrical conductivity of semiconductor increases when we add impurities and by increasing the temperature and it is contrary to the metals.
They have negative temperature Coefficient of resistance and which are formed by covalent bonds.
The electrical conduction in a semiconductor is due to free electrons in the conduction band and holes [vacant sites] in the valence band. The free electron current is in the opposite direction to the conventional current. But the hole current is in the same direction of the conventional current. The movement of the free electron and holes are in the opposite direction in the presence of applied field.
The total current in the semiconductor is the sum of the free electron current and hole current.
The free electrons and holes are produced by thermal ionization of atoms by means of breaking the covalent bonds due to applied voltage.
Mobility of the semiconductor
Mobility is defined as the ratio of drift velocity to the applied electric field.
\mu=\frac{V_d}{E}
Diffusion current of the semiconductor is defined as the motion of charge carriers from the region of higher concentration to the region of lower concentration
| Read More Topics |
| Fermi – Dirac distribution function |
| Energy distribution of electrons in metals |
| Numerical aperture and acceptance angle |
