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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This is a result of higher carrier mobilities and lower resistive device parasitics. However, there are pronounced differences to the case of a pn -junction in Si. Nobody knows how to do that in some kind of comprehensive theory. This then gives rise to three distinct cases for heterojunctions as illustrated below together with the necessary definitions of the various energies needed.
First, we align the Fermi energies. This type of heterojunction is sometimes called an isotype junctionthe pn -type a diode type junctions. 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.
But luckily, isotype junctions have similar properties: How, for example, does the precise nature of the discontinuities influence the current – voltage characteristics across a heterojunction? What happens if we join the two materials? GaAs-based devices hold the world record for the highest-efficiency single-junction solar cell at Consequently, GaAs thin films must be supported on a substrate material.
Silicon is a pure element, avoiding the problems of stoichiometric imbalance and thermal unmixing of GaAs. Below the conduction band structure of an advanced Al x Ga 1-x As device is shown to illustrate that point.
Isotype junctions must also have band discontinuities at the interface, the next picture shows examples. We also have the energy of the band edges, E C and E Vand from their difference the bandgap energy Gasa g. There are many heterojunctions and we will not be able to delve very deep into the subject. To the left and the right of the junction the bands are bend accordingly, and so is the vacuum energy.
Because GaAs and AlAs have almost the same lattice constantthe layers have very little induced strainwhich allows them to be grown almost arbitrarily thick. We must introduce a discontinuity istoype at the interface at one of the bands or at both. Concerns over GaAs’s susceptibility to heat damage have been 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.
Chichester, West Sussex, England: In the early s, the efficiency of the best GaAs solar cells surpassed that of conventional, crystalline silicon -based solar cells. Naturally, a GaAs surface cannot withstand the high temperatures needed for diffusion; however a viable and actively pursued alternative as of the ‘s was ion implanation.
Retrieved from ” https: Gallium arsenide single crystals can be prepared by three industrial processes: Silicon has three major advantages over GaAs for integrated circuit manufacture. GaAs can be used for various transistor types: There is, however, one feature of the discontinuities that makes life somewhat easier: If we look ahead, we can now easily denote multi-junctions like PnPand so on.
The situation with respect to moving carriers from 1 to 2 or vice verse is no longer symmetrical. Exactly the same thing as for differently doped Si:.
Gallium arsenide – Wikipedia
Extended isorype diode laser Volume Bragg grating laser. Refractive index n D. If we adjust the band bending on both sides so that the conduction bands match, the valence band won’t match and vice verse. In heterojunctions of the diode type, injection of the majority carriers from the material with the larger band gap almost always far surpasses the reverse process. The environment, health and safety aspects of gallium arsenide sources such as trimethylgallium and arsine and industrial hygiene monitoring studies of metalorganic precursors have been reported.
GaAs diodes can be used djode the detection of X-rays. Views Read Edit View history. Combined isotyype a high dielectric constantthis property makes GaAs a very good substrate for Integrated circuits and unlike Si provides natural isolation between devices and circuits.
Far away from the junction, everything is unchanged. Cray eventually built one GaAs-based machine in the early s, the Cray-3but the effort was not adequately capitalized, and the company filed for bankruptcy in Some electronic properties of gallium arsenide are superior to those of silicon.