Semiconductor Science and Technology vol:13 issue:3 pages:318-321
We have investigated the influence of the thickness of an undoped spacer layer under the channel an the current-voltage characteristics of GaAs MESFETs. To that purpose we have grown the active layers of the MESFETs on top of a 50 nm AlAs layer to separate the device effectively from the undoped GaAs substrate. Substrate leakage currents are of the order of 10(-7) A at 30 V source-substrate bias. DC characteristics are measured for four MESFETs with identical layer structure and doping but different spacer layer thicknesses. Comparison shows that MESFETs with thin spacer layers can he useful for low-noise applications but lose in transconductance and mobility values.