SEMICONDUCTORS

Semiconductors Materials
Atom
 All matters are made of atoms made of electrons,
protons and neutrons

 An atom is the smallest particle of an element and
each element has a unique atomic structure

 According to Bohr Model, atom structure has central
nucleus and orbiting electrons

 Each type of atom has a certain number of electrons
and protons different from atoms of other elements

Department of EE 1

, Atom

Orbiting
Electrons Nucleus
(- ve)

Protons
(+ve
)

Neutron
(Uncharge
s
d)
Department of EE 2

, Energy Levels
 Electrons orbit the nucleus of an atom at
certain distance from the nucleus
 Each orbit correspond to a certain
energy level
 Electrons near the nucleus has less
energy than those in more distant orbits
 The orbits are grouped into energy
bands known as shells

Department of EE 3

, Energy Levels….
 An atom has a fixed number of shells
 Each shell has a fixed maximum
number of electrons
 The shells are designated K, L, M, N, etc
from the nucleus
 Energy differences within shells are
much smaller than the energy
differences between shells
Department of EE 4