Q1-why copper is good conductor whereas silicon is semiconductor??Copper is a Good Conductor. Why?Materials that conduct electricity well, such as copper, are called conductors. Materials that do not conduct electricity well, such as glass, are called insulators. Semiconductors can act as insulators or conductors, depending on their construction and temperature.

Copper is one basic element that is represented by the chemical symbol, Cu. It is characterized to be ductile and was found to be great conductors of heat and electricity.The conducting power of copper makes it one of the most preferred electrical conductors, especially in construction of buildings and large infrastructures. Copper is a good conductor of electricity because of its huge charge density allowing more electrons to flow in its conducting system. This high charge density that copper possesses is the responsible for the slow drift of velocity that occurs when electrical charges are being discharged and transmitted. Among the many elements discovered and classified, copper is the most opted type of electrical conductor because aside from its high conductivity, it is found to be cheaper compared to the best conductor, silver.

Nowadays, copper is the most common material used for electrical wiring.Copper is physically characterized to be malleable and ductile that comes in reddish, orangish, or brownish color. These colors are attributed to a thin layer of tarnish that copper contains. Copper is commonly used for industrial and commercial purposes such as in electronics, architecture, agriculture, alloys and biomedical applications.Silicon is a semiconductor. Why?Silicon is a group IV element, and its valence energy band is exactly half filled with electrons (out of a possible 8 electrons, it has 4 in its valence band). By itself, it does not have many free electrons floating loosely about its crystal lattice and is a bad conductor. However, when doped with a group V element, of which the atoms replace some of the silicon atoms in the crystal lattice, a surplus of electrons are introduced that do NOT have a fixed place in the crystal lattice. These electrons may be caused to drift by an applied electric field, resulting in current flow, causing the silicon to act as a conductor. Similarly, if a group III impurity is added, it results in "holes" in the lattice. Electrons can jump from hole to hole and once again cause current flow.So, silicon in its pure state does not conduct electricity, but may be transformed into a conductor by adding impurities that cause a surplus of free charges that are not fixed in the lattice structure.

Q2-WHY silicon is widely used in semiconductor device as compared to Germanium? As we all know, both Silicon and Germanium are semiconductor devices. But the present trend is to use Silicon instead of Germanium because of the following reasons: At room temperature, Silicon crystal has fewer free electrons than Germanium crystal. This implies that silicon will have much smaller Collector cut off current than Germanium. The variation of Collector cut off current with temperature is less in Silicon compared to Germanium. The structure of Germanium crystals will be destroyed at higher temperature. However, Silicon crystals are not easily damaged by excess heat. Peak Inverse Voltage ratings of Silicon diodes are greater than Germanium diodes. Si is less expensive due to the greater abundance of element. The major raw material for Si wafer fabrication is sand and there is lots of sand available in nature.

But there is a disadvantage for Silicon over Germanium.The potential Barrier of Silicon is more compared to Germanium.But if we consider the advantages listed above, we can conclude that Silicon is the best element for the Semiconductor Devices and Applications.