03-12-2012, 12:01 PM
CONDUCTION IN SEMICONDUCTORS
[attachment=42221]
Electrons and holes in an intrinsic semiconductors, conductivity of a semiconductor, carrier concentrations in an intrinsic semiconductor, donor and acceptor impurities, charge densities in a semiconductor, Fermi level in a semiconductor having impurities, diffusion, carrier life time, Hall effect.
Atomic Structure
• Atom is the basic building block of all the elements. It consists of the central nucleus of positive charge around which small negatively charged particles called electrons revolve in different paths or orbits.
• An Electrostatic force of attraction between electrons and the nucleus holds up electrons in different orbits.
• Nucleus is the central part of an atom and contains protons and neutrons. A proton is positively charged particle, while the neutron has the same mass as the proton, but has no charge. Therefore ,nucleus of an atom is positively charged.
Positive and negative ions
• Protons and electrons are equal in number hence if an atom loses an electron it has lost negative charge therefore it becomes positively charged and is referred as positive ion.
• If an atom gains an electron it becomes negatively charged and is referred to as negative ion.
Free electrons
• The valence electrons of different material possess different energies. The greater the energy of a valence electron, the lesser it is bound to the nucleus.
• In certain substances, particularly metals, the valence electrons possess so much energy that they are very loosely attached to the nucleus.
• The loosely attached valence electrons move at random within the material and are called free electrons.
[attachment=42221]
Electrons and holes in an intrinsic semiconductors, conductivity of a semiconductor, carrier concentrations in an intrinsic semiconductor, donor and acceptor impurities, charge densities in a semiconductor, Fermi level in a semiconductor having impurities, diffusion, carrier life time, Hall effect.
Atomic Structure
• Atom is the basic building block of all the elements. It consists of the central nucleus of positive charge around which small negatively charged particles called electrons revolve in different paths or orbits.
• An Electrostatic force of attraction between electrons and the nucleus holds up electrons in different orbits.
• Nucleus is the central part of an atom and contains protons and neutrons. A proton is positively charged particle, while the neutron has the same mass as the proton, but has no charge. Therefore ,nucleus of an atom is positively charged.
Positive and negative ions
• Protons and electrons are equal in number hence if an atom loses an electron it has lost negative charge therefore it becomes positively charged and is referred as positive ion.
• If an atom gains an electron it becomes negatively charged and is referred to as negative ion.
Free electrons
• The valence electrons of different material possess different energies. The greater the energy of a valence electron, the lesser it is bound to the nucleus.
• In certain substances, particularly metals, the valence electrons possess so much energy that they are very loosely attached to the nucleus.
• The loosely attached valence electrons move at random within the material and are called free electrons.