Miniaturization

1
Miniaturization

• Primary Purpose

• - simply to provide some means of handling the
  device

• Advantages of current systems

• smaller and lightweight
• no heater requirement or heater loss
• more rugged construction
• more efficient
• not requiring a warm-up period

2
Limitations

• quality of the semiconductor material
  itself
• network design technique
• limits of the manufacturing and processing
  equipment

3
Definition of terms

• semi-

normally applied to a range of levels midway
between two limits

• CONDUCTOR

this term is applied to any material that will
support a generous flow of charge when a voltage
source of limited magnitude is applied across its
terminals
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Definition of terms

• INSULATOR

it is a material that offers a very low level of
conductivity under pressure from an applied
voltage source

• SEMICONDUCTOR

It is a material that has a conductivity level
somewhere between the extremes of an insulator
and a conductor
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• Inversely related

The higher the conductivity level, the lower the
resistance level

• Two materials used in the development of
  semiconductor devices

Germanium (Ge) and Silicon (Si)
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Reasons that Ge and Si have received the
attention

• They can be manufactured to a very high purity
  level

• The ability to change the characteristics of the
  material significantly through the process known
  as doping

• Their characteristics can be altered
  significantly through the application of heat or
  light

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Why do Ge Si have these characteristics?

• atomic structure

• the atoms of both materials form a very definite
  pattern that is periodic in nature

• Their characteristics can be altered
  significantly through the application of heat or
  light

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• one complete pattern is called a

• crystal

• periodic arrangement of the atoms

• lattice

• any material composed solely of repeating
  crystal structures of the same kind

• single-crystal structure

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INTRINSIC MATERIALS

• those semiconductors that have been carefully
  refined to reduce the impurities to a very low
  level

• when the temperature of a semiconductor is
  increased
• it can result to a substantial increase in the
  number of free electrons in the materials

• thereby increasing the conductivity index and
  result in a lower resistance level

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Positive vs. Negative Temperature Coefficient

• Negative Temperature Coefficient

• semiconductor materials such as Ge and Si that
  show a reduction in resistance with increase in
  temperature

• Positive Temperature Coefficient

• resistance of most conductors will increase w/
  temperature

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EXTRINSIC MATERIALS

• a semiconductor material that has been subjected
  to the doping process

• two types

• n-type

• p-type

• how is the n-type created?

• by introducing those impurity elements that have
  five valence electrons

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n-type

• pentavalent atoms

• antimony (Sb)

• arsenic

• phosphorus

• donor atoms

• diffused impurities with 5 valence electrons-
  since the inserted impurity atom has donated a
  relatively free electron to the structure

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p-type

• how is the p-type formed?

• by doping a pure germanium or silicon crystal
  with impurity atoms having three valence electrons

• trivalent atoms

• boron

• gallium

• indium

• hole

• absence of a negative charge

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p-type

• acceptor atoms

• diffused impurities with 3 valence electrons-
  called as such because the resulting vacancy will
  readily accept a free electron

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majority minority carriers

• n-type

• electron majority carrier

• hole minority carrier

• p-type

• hole majority carrier

• electron minority carrier

• n- and p-type materials

• represent the basic building blocks of
  semiconductor devices