We report on the successful molecular beam epitaxial (MBE) regrowth of a mo
dulation doped GaAs/AlGaAs two-dimensional electron gas (2DEG) only 160 Ang
strom from a patterned GaAs mesa with a (1.5 K) mobility, without illuminat
ion, of 1 x 10(5) cm(2) V-1 s(-1) at a carrier concentration of 5 x 10(11)
cm(-2). At a regrowth interface/2DEG separation of 300 Angstrom, mobilities
in excess of 1 x 10(6) cm2 V-1 s(-1) have been realised. By incorporating
a Si delta doped layer in the first GaAs growth and using this to modulate
the potential within a regrown 2DEG, we have demonstrated the growth of an
ultra short FET. (C) 1999 Elsevier Science B.V. All rights reserved.