Substrate effects on the threshold voltage of GaAs field-effect transistors

An array of field-effect transistors fabricated by direct ion implantation on a liquid-encapsulated-Czochralski (LEC) In0.003Ga0.997As wafer exhibits greater uniformity of threshold voltage than arrays on similarly processed conventional LEC GaAs wafers. However, there is no correlation between a transistor’s threshold voltage and its proximity to a dislocation for either In-alloyed or conventional LEC GaAs substrates. An observed correlation of threshold voltage with local dislocation density for GaAs substrates can lead to the erroneous inference that threshold voltage is affected by dislocation proximity.