  Semiconductor nanowires are believed to play a crucial role for future
applications in electronics, spintronics and quantum technologies. A potential
candidate is HgTe but its sensitivity to nanofabrication processes restrain its
development. A way to circumvent this obstacle is the selective area growth
technique. Here, in-plane HgTe nanostructures are grown thanks to selective
area molecular beam epitaxy on a semi-insulating CdTe substrate covered with a
patterned SiO$_{\mathrm{2}}$ mask. The shape of these nanostructures is defined
by the in-plane orientation of the mask aperture along the <$110$>,
<$1\bar{\mathrm{1}}0$>, or <$100$> direction, the deposited thickness, and the
growth temperature. Several micron long in-plane nanowires can be achieved as
well as more complex nanostructures such as networks, diamond structures or
rings. A good selectivity is achieved with very little parasitic growth on the
mask even for a growth temperature as low as $140${\deg}C and growth rate up to
$0.5$ ML/s. For <$110$> oriented nanowires, the center of the nanostructure
exhibits a trapezoidal shape with {$111$}B facets and two grains on the sides,
while <$1\bar{\mathrm{1}}0$> oriented nanowires show {$111$}A facets with
adatoms accumulation on the sides of the top surface. Transmission electron
microscopy observations reveal a continuous epitaxial relation between the CdTe
substrate and the HgTe nanowire. Measurements of the resistance with fourpoint
scanning tunneling microscopy indicates a good electrical homogeneity along the
main NW axis and a thermally activated transport. This growth method paves the
way toward the fabrication of complex HgTe-based nanostructures for electronic
transport measurements.
