  We report a method for growing rectangular InAs nanofins with deterministic
length, width and height by dielectric-templated selective-area epitaxy. These
freestanding nanofins can be transferred to lay flat on a separate substrate
for device fabrication. A key goal was to regain a spatial dimension for device
design compared to nanowires, whilst retaining the benefits of bottom-up
epitaxial growth. The transferred nanofins were made into devices featuring
multiple contacts for Hall effect and four-terminal resistance studies, as well
as a global back-gate and nanoscale local top-gates for density control. Hall
studies give a 3D electron density $2.5~-~5 \times 10^{17}$ cm$^{-3}$,
corresponding to an approximate surface accumulation layer density $3~-~6
\times 10^{12}$ cm$^{-2}$ that agrees well with previous studies of InAs
nanowires. We obtain Hall mobilities as high as $1200$ cm$^{2}$/Vs,
field-effect mobilities as high as $4400$ cm$^{2}$/Vs and clear quantum
interference structure at temperatures as high as $20$ K. Our devices show
excellent prospects for fabrication into more complicated devices featuring
multiple ohmic contacts, local gates and possibly other functional elements,
e.g., patterned superconductor contacts, that may make them attractive options
for future quantum information applications.
