  A junction between an n- and p-type semiconductor results in the creation of
a depletion region whose properties are at the basis of nowadays electronics.
If realized using topological insulators as constituent materials, p-n
junctions are expected to manifest several unconventional effects with great
potential for applications. Experimentally, all these fascinating properties
remained unexplored so far, mainly because prototypical topological PNJs, which
can be easily realized and investigated, were not readily available. Here, we
report on the creation of topological PNJs which can be as narrow as few tenths
of nm showing a built-in potential of 110meV. These junctions are intrinsically
obtained by a thermodynamic control of the defects distribution across the
crystal. Our results make Bi2Te3 a robust and reliable platform to explore the
physics of topological p-n junction.
