A high-transconductance self-aligned GaAs MESFET fabricated by through-AlN implantation

A new technique for the fabrication of high-transconductance GaAs MESFET's is described. Tungsten-silicide gate, self-aligned GaAs MESFET's were fabricated on extremely thin channel layers formed by implantation through AlN layers on semiinsulating GaAs substrates. Transconductance of the through-implanted MESFET's showed 30- to 50-percent increase as compared with that of conventional self-aligned MESFET's and reached its maximum value at 300 mS/mm for 1-micron gate-length FET's. The uniformity of the threshold voltage across a 2-in. wafer was also excellent with a standard deviation of 44 mV. Circuit simulation indicates that the advantage of these FET's becomes more crucial when used in a very large-scale integrated circuit (VLSI).