Semiconductor systems are actually electronic components that take advantage of the electronic properties of the semiconductor materials like silicon, germanium, and gallium arsenide. With the invention of the semiconductor devices have replaced most of the most of the vacuum tube applications. The replaced semiconductor system uses solid state instead of thermionic or gaseous state in a high vacuum.
A semiconductor device is manufactured as either single discrete device or as integrated circuits. The integrated circuits contain a few number to a few million devices interconnected to a single semiconductor substrate. The reason why the semiconductor materials are used in manufacturing most devices is that the behavior of a semiconductor can easily be controlled by adding impurities which is otherwise called as doping. Conduction in a semi conductor occurs through free electrons which on the whole are called as the charge carriers.
By using the doping technique one can increase the number is free electrons within the semiconductor. After doping when the semiconductor contains many free electrons, it is called as the n-type and when the semiconductor forms number of wholes it is called as the p-type. A semiconductor material is generally doped under extremely controlled conditions in a fabrication facility to control the location and concentration of the dopant. The junction where the p-type and n-type semiconductor join together is called as the pn junction.
So far silicone was widely used material in the semiconductors industry. This is due to the low cost and the simple usage and useful temperature range which makes silicone the most preferred material in the semiconductor systems. Earlier Germanium was used widely but after the invention of silicon germanium was replaced since the germanium material's thermal sensitivity makes it less productive and useful. However germanium is used alloyed with silicone, which is used in high speed SiGe devices.
Gallium Arsenide is also widely used mainly in high speed devices but due to the limitations of the material silicon is preferred by most manufacturers. The other materials that are widely used are Silicon carbide and various other indium components like indium arsenide, indium antimonide, and indium phosphide are also used in LED's and solid state laser diodes. Selenium sulfide is now taken into consideration to be used in semiconductor systems for the manufacturing of photovoltaic solar cells.
A list of Surplus Semiconductor Equipment and devices includes Avalanche diode, DIAC, Diode, Gunn diode, IMPATT diode, Laser diode, Light-emitting diode, Photocell, PIN diode, Schottky diode, Solar cell, Tunnel diode, VCSEL, VECSEL, Zener diode are two terminal devices. The three terminal devices includes Bipolar transistor, Darlington transistor, Field effect transistor, GTO, IGBT, SCR (Silicon Controlled Rectifier), SGCT (Switched Gate Commuted Thyristor), Thyristor, TRIAC, Unijunction transistor. The four terminal devices includes Hall Effect sensor (magnetic field sensor), Multi-terminal devices comprises of Charge-coupled device (CCD), Microprocessor, Random Access Memory (RAM), Read-only memory (ROM) and the list goes on.