Basics of semiconductor

 Basics of semiconductor

what is semiconductor?

      A semiconductor is a material that has intermediate conductivity between a conductor and an insulator. It means that it has unique physical properties somewhere in between a conductor like aluminum and an insulator like glass.As its name suggests,a semiconductor features resistivity levels on a range between those of a  conductor and an insulator. 
       semiconductor resistivity usually falls in between 10^-4 and 10⁴ ohms per centimeter

       Low electrical conductivity at room temperature,electrical conductivity increases with temperature.

Types of semiconductor: 

          Semiconductors are mainly classified into two categories.

Intrinsic semiconductor: An intrinsic semiconductor material is chemically very pure and possesses poor conductivity. It has equal numbers of negative carriers (electrons) and positive carriers (holes).

Extrinsic semiconductor: An extrinsic semiconductor is an improved intrinsic semiconductor with a small amount of impurities added by a process, known as doping, which alters the electrical properties of the semiconductor and improves its conductivity. 

 Doping process produces two groups of semiconductors: the negative charge conductor (n-type) and the positive charge conductor (p-type).The most common n-type dopants for silicon are phosphorus and arsenic, while the most common p-type dopant for silicon is boron.

 Semiconductors are available as either elements or compounds. Silicon and Germanium are the most common elemental semiconductors. Compound Semiconductors include InSb, InAs, GaP, GaSb, GaAs, SiC, GaN. 
List of semiconductor devices: 
     Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors.
       Semiconductor devices can be categorized depends upon the terminals
                 Two terminal devices:
                                        DIAC
                                        Diode
                                        Light-emitting diode  
                                        Photo cell
                                        Solar cell
                 Three terminal devices:
                                        TRIAC
                                         Bipolar transistor 
                                         Darlington transistor
                                         Field-effect transistor
                                         Silicon-controlled rectifier
                                         Unijunction transistor
                                         Insulated-gate bipolar transistor
                  Four terminal devices:

                                          Hall effect sensor

                 Multi terminal devices:   

                                          Integrated circuit(ICs)
                                          Charge-coupled device
                                          Microprocessor
                                          Random-access memory(RAM)
                                          Read-only memory(ROM)