Band gap

In semiconductor physics

In semiconductors and insulators, conduction band; electrons are able to jump from one band to another.

The intrinsic semiconductors is strongly dependent on the band gap. The only available carriers for conduction are the electrons which have enough thermal energy to be excited across the band gap.

Band gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor laser diodes and solar cells.

The distinction between semiconductors and insulators is a matter of convention. One approach is to consider semiconductors a type of insulator with a low band gap. Insulators with a higher band gap, usually greater than 3 eV, are not considered semiconductors and generally do not exhibit semiconductive behaviour under practical conditions. Electron mobility also plays a role in determining a material's informal classification.

Band gaps depend on temperature because of direct or indirect bandgaps, depending on the band structure.

Mathematical interpretation

Classically, the ratio of probabilities that two states with an energy difference ΔE will be occupied by an electron is given by the Boltzmann factor:

$e^{\left(\frac{-\Delta E}{kT}\right)}$

where:

e is the exponential function

$\, \Delta E$ is the energy difference

$\, k$ is Boltzmann's constant

$\, T$ is temperature

At the chemical potential), the probability of a state being occupied is ½. If the Fermi level is in the middle of a band gap of 1 eV, this ratio is e ^-20 or about 0.5•10^-9 at the room-temperature thermal energy of 25 meV.

List of band gaps

Material	Symbol	Band gap (eV) @ 300K
Silicon	Si	1.11 ^[1]
Germanium	Ge	0.67 ^[1]
Silicon carbide	SiC	2.86 ^[1]
Aluminum phosphide	AlP	2.45 ^[1]
Aluminum arsenide	AlAs	2.16 ^[1]
Aluminium antimonide	AlSb	1.6 ^[1]
Aluminium nitride	AlN	6.3
Diamond	C
Gallium(III) phosphide	GaP	2.26 ^[1]
Gallium(III) arsenide	GaAs	1.43 ^[1]
Gallium(III) nitride	GaN	3.4 ^[1]
Gallium(II) sulfide	GaS	2.5 (@ 295 K)
Gallium antimonide	GaSb	0.7 ^[1]
Indium(III) phosphide	InP	1.35 ^[1]
Indium(III) arsenide	InAs	0.36 ^[1]
Zinc sulfide	ZnS	3.6 ^[1]
Zinc selenide	ZnSe	2.7 ^[1]
Zinc telluride	ZnTe	2.25 ^[1]
Cadmium sulfide	CdS	2.42 ^[1]
Cadmium selenide	CdSe	1.73 ^[1]
Cadmium telluride	CdTe	1.58 ^[1]
Lead(II) sulfide	PbS	0.37 ^[1]
Lead(II) selenide	PbSe	0.27 ^[1]
Lead(II) telluride	PbTe	0.29 ^[1]

In photonics and phononics

In photonic crystal.

Similar physics applies to phononic crystal.

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u Streetman, Ben G.; Sanjay Banerjee (2000). Solid State electronic Devices, 5th edition, New Jersey: Prentice Hall, 524. ISBN 0-13-025538-6.

Band gap

In semiconductor physics

Mathematical interpretation

List of band gaps

In photonics and phononics

References

See also

Chemicals

List of electronics topics