文档介绍：Chapter 1: Semiconductor Basis and Diodes
Dr Yonghua Li
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coursework: 25%
experiments:15%
final exam: 60%
Principles of Semiconductors
Common materials used in the development of semiconductor devices:
Silicon (Si)
Germanium (Ge)
GaAs
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Principles of Semiconductors
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Covalent bonding of the silicon atom.
Intrinsic semiconductor: The single-crystal formed by pure semiconductor materials
Holes: Vacancies in the covalent bond
Electron-hole pairs: a free electron and a hole is generated from the covalent bond by thermal energy
The free electrons and holes in a material due only to external causes are referred to as intrinsic carriers
Intrinsic Semiconductors
Two types of charged particles (Intrinsic carriers) in a
semiconductor
free electrons
holes
semiconductor
Intrinsic Carriers (/cm3) @ room T.
GaAs
×106
Si
×1010
Ge
×1013
Semiconductor materials have a negative temperature coefficient
Intrinsic Semiconductors
Intrinsic Semiconductors
Movement of Holes: by movement of covalent electrons from adjacent covalent bonds
Electrical conductivity of intrinsic semiconductors is determined by the concentration of free electrons and holes
Extrinsic Semiconductors: N type and P type
The electrical characteristics of intrinsic semiconductors are improved by adding impurity materials in a process called doping.
The materials containing impurity atoms are called extrinsic semiconductors, or doped semiconductors.
There are just two types of doped semiconductor materials:
N type: impurities are from group V elements, . Phosphorus
P type: impurities are from group III elements, . Boron
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(1) N-type Semiconductors and Carriers
A semiconductor that contains donor impurity atoms is called a N-type semiconductor.
Impurities in N type materials act as Donor.
The minority carriers in N type materials are holes.
The majori