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Gainas was an ambitious Gothic leader who served the Eastern Roman Empire during the reigns of Theodosius I and Arcadius.

Gainas began his military career as a common foot-soldier, but later commanded the barbarian contingent of Theodosius' army against the usurper Eugenius in 394. In 395, he combined his forces with those of Stilicho and Eutropius to bring about the fall of Rufinus. In 399 he replaced the Magister Militum Leo after the latter failed to put down invasions led by Ostrogothic chieftain Tribigild. Gainas too failed to put down the invasions, although he blamed his failure on Eastern Roman Emperor Arcadius' palace chamberlain (cubicularius) Eutropius, whom he had executed.

Frustrated further by his inability to control the situation, Gainas ordered the removal of more ministers. Gainas' compromises with Tribigild led to rumors that he had colluded with his fellow Goth and, when he returned to Constantinople in 400, riots broke out and 7,000 of his fellow Goths were murdered by the populace who had been incited to action by the Empress Aelia Eudoxia.

In response, Gainas and his forces attempted to flee back across the Hellespont, but their rag-tag fleet was met and destroyed by a third Gothic chieftain, Fravitta. After this battle, Gainas and his few remaining forces were caught by the Huns under Uldin while trying to escape north of the Danube. Gainas was killed and his head was sent by Uldin to Arcadius ca. 400 as a gift.

Gainas' usurpation is the subject of the Egyptian Tale and the speech On Imperial Rule by Synesius of Cyrene.

Sources

Alan Cameron and Jacqueline Long, Barbarian and Politics at the Court of Arcadius, Berkeley et Los Angeles, 1993.
Alexander Kazhdan (éd.), The Oxford Dictionary of Byzantium, 3 vols., Oxford University Press, 1991 (ISBN 0-19-504652-8)
(fr) André Piganiol, L'Empire chrétien, PUF, Paris, 1972.

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Indium gallium arsenide (InGaAs) is a semiconductor composed of indium, gallium and arsenic. It is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide. InGaAs bandgap also makes it the detector material of choice in optical fiber communication at 1300 and 1550 nm. Gallium indium arsenide (GaInAs) is an alternative name for InGaAs.

The indium content determines the two-dimensional charge carrier density.

Properties

The optical and mechanical properties of InGaAs can be varied by changing the ratio of In and Ga, In_xGa_1−xAs. The InGaAs device is normally grown on an indium phosphide (InP) substrate. In order to match the lattice constant of InP and avoid mechanical strain, In_0.53Ga_0.47As, this composition has a cut-off wavelength of 1.68 μm.

By increasing the ratio of In further compared to As it is possible to extend the cut-off wavelength up to about 2.6 µm. In that case special measures have to be taken to avoid mechanical strain from differences in lattice constants.

GaAs is lattice mismatched to Ge by 0.08%. With the addition of 1.5% In to the alloy, InGaAs, becomes perfectly latticed matched to Ge. The complete elimination of film stress reduces the defect densities of the epi InGaAs layer compared to straight GaAs.

Applications

HEMT devices using InGaAs channels are one of the fastest types of transistor .

InGaAs is also a popular material in infrared detectors. It is widely replacing germanium as a detector material mainly due to lower dark current (internally generated current). It is used as the detector material in some short-wave infrared cameras. InGaAs also has lower multiplication noise than germanium when used as the active multiplication layer of an avalanche photodiode.

InGaAs can be used as a laser medium. Devices have been constructed operating at wavelengths of 905 nm, 980 nm, 1060 nm, and 1300 nm. InGaAs quantum dots on GaAs have also been studied as lasers.

In(.015)Ga(.985)As can be used as an intermediate band-gap junction in multi-junction photovoltaic cells with a perfect lattice match to Ge. The perfect lattice match to Ge reduces defect density, improving cell efficiency.

Safety and toxicity aspects

The toxicology of InGaAs has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of indium gallium arsenide sources (such as trimethylgallium, trimethylindium and arsine) and industrial hygiene monitoring studies of standard MOVPE sources have been reported recently in a review .