Improved breakdown voltage in GaAs MESFETs utilizing surface layers of GaAs grown at a low temperature by MBE

A metal-semiconductor field-effect transistor (MESFET) utilizing surface layers of GaAs grown at a low temperature by MBE (LT GaAs) under the gate electrode has been fabricated. The high trap density of LT GaAs reduces the surface fields of the FET, suppresses gate leakage, and increases the gate-drain breakdown voltage without sacrificing current drive capability. An undoped AlAs layer is incorporated between the LT GaAs layer and the channel as a barrier to the diffusion of excess As from the LT GaAs layer to the channel. A 74- mu m-gate-width device demonstrated an improved breakdown voltage of 34.85 V with a g/sub m/ of 144 mS/mm and an I/sub dss/ of 248 mA/mm.<
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