Semiconductors are materials whose conductivity falls between conductors and insulators. They have a valence band, conduction band, and forbidden energy gap. Solids are classified as conductors, insulators, or semiconductors based on the relationship between these bands. Intrinsic semiconductors have low conductivity, while extrinsic semiconductors are doped with impurities to increase conductivity, making them either N-type with extra electrons or P-type with extra holes.

1. INTRODUCTION TO
SEMICONDUCTORS
HAREESH.S.
PHYSICAL SCENCE
Hareesh.s.
Physical science
Reg.no : 18214383009

2. ELECTRONICS
Electronics is the branch of physics
deals with the current conduction
through vacuum , gas or semi
conductor

3. ENERGY LEVELS
Valence band (VB) :- the range of energy possessed by valence
electrons
Conduction band(CB) :- the range of energy possessed by
conduction electrons.
Forbidden energy gap (Eg) :- energy difference between VB &
CB.

4. SOLIDS - CLASSIFIED IN TO THREE
CONDUCTOR { VB & CB are
overlapped }
INSULATOR { Eg ≥5 eV }
SEMI CONDUCTOR { Eg≈1eV }

5. INTRINSIC SEMI CONDUCTORS & EXTRINSIC
SEMI CONDUCTORS
Pure semiconductors are known as intrinsic
semiconductors
eg: Si,Ge..
Intrinsic semi conductor has low conductivity at 0K
DOPING :- process of adding impurity to increase the
conductivity of intrinsic semi conductor
Semiconductor having impurity is known as extrinsic semi
conductor

6. EXTRINSIC SEMI CONDUCTORS ARE
AGAIN CLASSIFIED IN TO TWO ;
N-TYPE SEMI CONDUCTORS
AND
P-TYPE SEMI CONDUCTORS

7. N - type semi conductors
Doped with penta valent atoms like arsenic
,antimony,phosphorus
or bismuth
Electrons majority carriers & holes minority
carriers

8. P - type semi conductors
Doped with tri valent atoms like boron ,indium
,gallium ,thallium..
Holes are majority carriers and electrons are
,majority charge carriers