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Pseudomorphic High Electron Mobility Transistor
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A field effect semiconductor device where complex metalization
structures are used to create a junction with higher electron
mobility than can be achieved in pure Gallium Arsenide. In
simplistic terms, PHEMTs provide a way to get the high mobility
of Indium Phosphide on a Gallium Arsenide substrate, thereby
avoiding the breakage problems associated with the very brittle
Indium Phosphide wafers. The term "pseudomorphic" - literally
"false form" - comes from the fact that the very thin
semiconductor layer used to form the junction abandons its
customary crystal lattice structure and assumes the form of the
underlying GaAsS substrate, thus creating a mechanically viable
structure.
PHEMT technology is most commonly used to make ultra-low
noise devices such as those used in the DBS market, or to make
devices for operation at millimeter wave frequencies (i.e. above 20
GHz).
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