Semiconductor Materials Characteristics

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Melting Points of Different Semiconductor Materials

Property Si Ge GaAs SiO2
Melting Point Celcius 1412 937 1238 ~1700
Atomic Weight 28.09 72.6 144.63 60.08
Atomic density (atoms/cm3) 4.00 x 10 to the 22 4.42 x 10 to the 22 2.21 x 10 to the 22 2.3 x 10 to the 22
Energy Band GaP (eV) 1.11 0.67 1.40 ~8

 

Semiconductor Materials Characteristics

As of today, Silicon (Si) is still the most important material used in Si icon. Silicon wafers are used to fabricate devices. Si's unique physical and chemical properties provide the semiconductor industry with a cheap and abundant supply.

Silicon's Atomic Structure

Silicon's atomic structure includes the following:

  • Electrons
  • Protons
  • Neutrons

Silicon on the Periodic Table

Silicon, although abundant, is not found in pure form. Si must be purified by refining it.

The melting point of Silicon 1412 deg C.

Pure Silicon is called Intrinsic Silicon and it has no impurities.

An example of Intrinsic Silicon specs are as follows:

100mm Intrinsic FZ Si (100) >20,000 ohm-cm 500um SSP

Silicon makes up around 85% of the material used in Semiconductors. But why Silicon and not another material?

Why Use Silicon in Semiconductors?

Below are the main reasons why Silicon and not Germanium, the first semiconductor, is used in semiconductors.

  • Silicon is the second most abundant material on earth after carbon. Silicon makes up 25% of the earth crust.
  • Silicon has a higher melting point to withstand higher processing temps.
  • Silicon has a wider range of temperatures that it can function under. So from cold to hot, Silicon performance surpasses most other materials such as Germanium.
  • Silicon dioxide (SiO2) grows naturally on the surface of Silicon Wafers. SiO2 is stable insulator required in semiconductors. The mechanical properties of SiO2 means you can process the wafer at high-temp without the wafer warping.

Silicon Dioxide on Silicon Wafer

Doping Silicon

Not only can Silicon be purfied to make it Intrinsic, silicon can also be doped to create Extrinsic Silicon.

So extrinsic silicon is impure. But it's done on purpose to increase semiconductor conductivity.

Adding impurities or doping can change the electrical conductivitiy of the semiconductor.

Doped Silicon Resistivity

Doping pure silicon reduces resistivity while it improved conductivity.

Silicon pn Junctions

The heart of solid-state electronics is the pn junction. Pn junctions and is the reason why semiconductors can act as both an insulator and as a conductor.