Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III-V direct . GaAs diodes can be used for the detection of X-rays. Type I heterojunctions are quite common, the important GaAs – AlGaAs system is sometimes called an isotype junction, the pn-type a diode type junctions. The double-Schottky-diode model of Oldham and Milnes. The l-V characteristics of the GaAs-Ge isotype heterojunctions investigated by Anderson .
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The simplest model called the Anderson model assumes that D E C is equal to the difference in the electron affinities c.
We now have a degree of freedom for all heterojunctions, which did not occur for homojunctions: Isotype junctions must also have band discontinuities at the interface, the next picture shows examples.
We must introduce a discontinuity right at the interface at one of the bands or at both. This page was isotypd edited on 27 Novemberat This is a very important equation for optoelectronics.
The hole and electron part of the total current now are different even for a perfectly symmetric junction! Gallium arsenide single crystals can be prepared by three industrial processes: How can we find the real case?
Refractive index n Diide. Again, a discontinuity like this must happeneven at “ideal” interfaces. Gallium arsenide GaAs is a compound of the elements gallium and arsenic. Wikimedia Commons has media related to Gallium arsenide.
This allows extremely high performance and high electron mobility HEMT transistors and other quantum well devices. Because GaAs diodde AlAs have almost the same lattice constantthe layers have very little induced strainwhich allows them to be grown almost arbitrarily thick.
From Wikipedia, the free encyclopedia. The economies of scale available to the silicon industry has also hindered the adoption of GaAs. If you think about that a minute and try to come up with some structure, you will realize, that there is a problem: For homojunctionsthe number of electrons flowing into the p -type part is then the same as the number of electrons flowing into the n -part. How, for example, does the precise nature of the discontinuities influence the current – voltage characteristics across a heterojunction?
In reality, the matching of two lattice types with different atoms on both sides may well introduce some interface states in the bandgap, as discussed for the free Si surface.
First, silicon is abundant and cheap to process in the form of silicate minerals. These superior properties are compelling reasons to use GaAs circuitry in mobile phonessatellite communications, microwave point-to-point links and higher frequency radar systems. One possible reason was already mentioned: First, we align the Fermi energies. Inthe GaAs heterostructure solar cells were developed by the team led by Zhores Alferov in the USSR[17] [18] [19] achieving much higher efficiencies.
Lets first look at the basic cases that we may encounter when considering heterojunctions. It is also used in the gaass of Gunn diodes for the generation of microwaves. Concerns over GaAs’s susceptibility to heat damage have isohype raised, but it has been speculated that certain manufacturers would benefit from such limitations, considering the planned obsolescence cycle that many consumer electronics are designed to follow.
Silicon is a pure element, avoiding the problems of stoichiometric imbalance and thermal unmixing of GaAs.
As a wide direct band gap material with resulting resistance to radiation damage, GaAs is an excellent material for outer space electronics and optical windows in high power applications.
However, there are pronounced differences to the case of a pn -junction in Si. Such good mechanical characteristics also make it a suitable material for the rapidly developing field of nanoelectronics.
Gallium arsenide
The surface can be passivated by depositing a cubic gallium II sulfide layer using a tert-butyl gallium sulfide compound such as t BuGaS 7. How do we measure the values of the discontinuities? The bandgaps do not overlap at all. There are many heterojunctions and we will not be able to delve very deep into the subject. This simply means that its value does not change much if we change properties of the materials on a scale much larger than the atomic scale.
Gaas Isotype Diode Pdf Download
GaAs can be used for various transistor types: Also many solar cars utilize GaAs in solar arrays. Views Read Edit View history. Exactly the same thing as for differently doped Si:. We can not join the two materials!
Gallium arsenide – Wikipedia
How do we construct a band diagram? If D E g is sufficiently large – and since it is in an exponential term, it does not have to be very large – it will always overwhelm the possible asymmetries in the pre-exponential term, e. We also must specify the exact position on the energy scale of one of the band edges. Below the conduction band structure of an advanced Al x Ga 1-x As device is shown to illustrate that point. For the intrinsic carrier concentrations of any semiconductor we have the basic equations:.
The Chemistry of the Semiconductor Industry. Transparency to light generated in some active part. In contrast, the absorptivity of GaAs is so high that only a few micrometers of thickness are needed to absorb all of the light.