DEFINATION AND OTHER ABOUT ELECTRONICS

Q.1: What do you mean by semiconductor?

Ans: Semiconductor: Semiconductor is special class of elements having conductivity between that of a good conductor and an insulator.

Semiconductor materials are two classes:

1. Single - crystal: Single crystal semiconductors such as germanium (Ge) and silicon (Si) have a repetitive crystal structure.


2. Compound: Compound semiconductors such as gallium arsenide (GaAs), cadmium sulfide (Cads), gallium nitride (GaN), and gallium arsenide phosphide (GaAsP) are constructed of two or more semiconductor materials of different atomic structures.

Semiconductor materials have a negative temperature coefficient. Pure semiconductor is an insulator. Three semiconductors used most frequently in the construction of electronic devices are Ge, Si, and GaAs.

Q.2: What do you mean by doping?

Ans: Doping: The characteristics of semiconductor materials can be altered significantly by the addition of a small controlled amount of impurity atoms into the pure semiconductor. The process by which this can be happened is called doping.

Q.3: Define valence electrons and covalent bonding.

Ans: Valence electron: Every atom is composed of three basic particles: the electron, the proton and the neutron. In the lattice structure neutrons and protons form the nucleus and electrons appear in fixed orbits around the nucleus. The Bohr model for the three materials is provided in fig bellow. Valance electron

Fig: Silicon and Germanium

In the fig silicon has 14 orbiting electron, germanium has 32 orbiting electrons. Here germanium and silicon has four electrons in the outermost shell which are referred to as valence electrons.

So we can say, in an atomic structure the outer most shell is known as valence electron which can remove from that shell.

Covalent bonding: In the atomic structure when valence electron and their parent atom create bonding by the sharing of electrons, is called covalent bonding. Covalent bond is stronger between the valence electrons and parent atom.

In a pure silicon or germanium crystal four valence electrons of one atom from a covalent bonding arrangement with four adjoining atoms in the fig.

GaAs is a compound semiconductor, there is sharing between the two different atoms, as shown in above.