Gac. Jones et al., GAAS ALGAAS DEVICE FABRICATION USING MBE GROWTH AND IN-SITU FOCUSED ION-BEAM LITHOGRAPHY/, Physica. B, Condensed matter, 227(1-4), 1996, pp. 264-267
We describe a versatile technique for the fabrication of 3-D patterned
III-V semiconductor devices, using molecular beam epitaxial (MBE) gro
wth and high energy focused ion beam (FIB) lithography. Ohmic contacts
can be made independently to a 2DEG and a closely separated n(+) GaAs
backgate by first implanting regions of the backgate which will event
ually lie directly below the ohmic contacts to the 2DEG, rendering the
m highly resistive. Conventional technology can then be used to form o
hmic contacts to the 2DEG, resulting in very high device yields (>80%)
, compared to those utilising a shallow ohmic contacting process. Furt
her, no deterioration of the 2DEG quality is observed, despite the gro
wth interruption during ion beam patterning. This technique has been f
urther developed to pattern the back-gate into multiple conducting and
insulating regions, e.g. a split-gate geometry patterned on the back-
gate or, using a combination of FIB patterned backgates and Schottky f
ront-gates, the formation of independent contacts to two closely space
d ( <10 nm) 2DEGs.