III-V compound semiconductors

group	13	14th	15th
period				Bowl
2	5 B		7 N.	L.
3	13 Al		15 p	M.
4th	31 Ga		33 As	N
5	49 in		51 Sb	O

Main group III / V from the periodic table

A III-V compound semiconductor is a combination of materials from the main chemical group III (earth metals / boron group) and V (nitrogen-phosphorus group) , the combination of which has the electrical conductivity of semiconductors . III-V compound semiconductors are therefore of great importance for technical applications in semiconductor technology .

III-V compound semiconductors can be used to generate light with very short wavelengths ( UV range) using laser diodes or LEDs (applications: white light-emitting diode , Blu-ray Disc , HD DVD . See Shuji Nakamura ). Conversely, the material is also suitable for the production of solar cells with a very high degree of efficiency (over 40%).

Representative

High purity indium antimonide (InSb) for semiconductor applications.

• Nitrides : gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), boron nitride (BN)

The natural crystallization of nitrides is the wurtzite structure. Zinc blende formations can also be created using special techniques . In addition, the chemical structure of rock salt exists even under very high atmospheric pressure .

• Phosphides : gallium phosphide (GaP), aluminum phosphide (AlP), indium phosphide (InP), indium gallium phosphide (InGaP), boron phosphide (BP)
• Arsenides : gallium arsenide (GaAs), aluminum arsenide (AlAs), indium arsenide (InAs), boron arsenide (BAs)
• Antimonides : Gallium antimonide (GaSb), aluminum antimonide (AlSb), indium antimonide (InSb)

In principle, these compounds crystallize in the zinc blende structure .

The binary material compounds contain (in the case of undoped material) atoms of group III and V in equal proportions. However, mixed forms can be created within the groups in which the proportion of Group III or Group V atoms is composed of two types of atoms. This creates ternary (a total of three types of atoms) and quarternary (four types of atoms) compounds. Examples of ternary compounds are aluminum gallium arsenide , indium gallium nitride and indium gallium arsenide . An example of a quaternary compound is . ${\displaystyle \mathrm {Ga} _{1-x}\mathrm {In} _{x}\mathrm {As} _{1-y}\mathrm {P} _{y}}$

Manufacturing

III-V compound semiconductors are produced almost exclusively by epitaxial growth . For the individual epitaxy processes, the substances are mostly in gaseous form and in this state are highly toxic even in small quantities.

properties

Band gap plotted over the lattice constant . The lines between the elements represent the ternary connections. The wurtzite crystallizations have two lattice constants a and c, the zinc blende only one.

Compound semiconductors from main group III and V have the great advantage over silicon that their band gap can be varied with the material composition. The electrical properties can thus be changed in a targeted manner. They mainly find technical applications in optical devices such as detectors , light-emitting diodes or lasers . In addition, some connections have a direct band transition (see band gap , band diagram ), which favors their use in optical applications.

One important material parameter is therefore the band gap energy. It determines which wavelength of light ( photons ) can be generated or absorbed in optical applications. On the other hand, the lattice constant of the material plays a role. Since the semiconductors can only be produced by epitaxial growth, the materials must be matched to one another. Differences in the lattice constant can, on the one hand, generate piezoelectric charges in the material, form recombination centers through dangling bonds , and provoke breaks and cracks.

Calculation of the ternary lattice constants

For the lattice constants of ternary mixed compounds, mostly linear transitions are assumed. This is known as Vegard's rule and reads for the lattice constant a of the mixed crystal A _x B _1-x Z from the atoms A, B, Z:

${\displaystyle a(A_{x}B_{1-x}Z)=x\cdot a(AZ)+\left(1-x\right)\cdot a(BZ)}$

Lattice constants (in Å = 10 ⁻¹⁰ m) of selected binary compounds at room temperature

	Zinc cover				Wurtzit
	P	As	Sb	N
	a	a	a	a	a	c
Al	5.4510	5.6605	6.1355	-	3.112	4,982
Ga	5.4512	5.6533	6.0959	4.520	3.189	5.185
In	5.8686	6.0584	6.4794	-	3.545	5.703

Calculation of the ternary band transition energies

In contrast, a quadratic term is used to calculate the band transition energies E _g . With this term, the experimentally determined values ​​are approximated as closely as possible to a curved curve. The constant additional terms for hot diffraction parameters (ger .: bowing parameter ). ${\displaystyle C}$

${\displaystyle E_{\mathrm {g} }(A_{x}B_{1-x}Z)=x\cdot E_{\mathrm {g} }(AZ)+(1-x)\cdot E_{\mathrm {g} }(BZ)+x\cdot (1-x)\cdot C(A_{x}B_{1-x}Z)}$

See also

• II-VI compound semiconductors
• Wide band gap semiconductors

literature

• I. Vurgaftman, JR Meyer, LR Ram-Mohan: Band parameters for III-V compound semiconductors and their alloys. In: Journal of Applied Physics. 89, 2001, p. 5815, doi: 10.1063 / 1.1368156 .
• I. Vurgaftman, JR Meyer: Band parameters for nitrogen-containing semiconductors. In: Journal of Applied Physics . 94, 2003, p. 3675, doi: 10.1063 / 1.1600519 .

Web links

• Physical data of some III-V semiconductors, Ioffe-Institut St.Petersburg, engl.
• Java applet for calculating the band gaps of the ternary connections, engl.

Individual evidence

1. ↑ World record: 41.1% efficiency for multiple solar cells at Fraunhofer ISE. (No longer available online.) In: Press information 01/09. Fraunhofer ISE, January 14, 2009, archived from the original on August 13, 2011 ; Retrieved January 22, 2010 . 
2. ↑ L. Vegard: The constitution of mixed crystals and the space filling of the atoms. In: Z. Phys. 5, No. 1, 1921, pp. 17-26, doi: 10.1007 / BF01349680 .