Self-aligned modulation-doped (Al,Ga)As/GaAs field-effect transistors

The first modulation-doped (Al,Ga)As/GaAs field-effect transistors (MODFET's) have been fabricated using a self-aligned ion-implantation process. Measured extrinsic transconductances of 190 mS/mm were achieved at 300 K with source resistances of 1 Ω.mm. The highest currents yet reported for such device structures, in excess of 350 mA/mm, were obtained. A value of the maximum two-dimensional electron gas concentration of nearly 1.2 × 10
¹²
cm
^-2
was obtained from an analysis of the FET drain current-voltage characteristics using the charge-control model. These results hold promise for the practical fabrication of very high speed integrated circuits based on MODFET's, using a completely planar self-aligned ion-implantation process.