  Defects in wide bandgap semiconductors have recently emerged as promising
candidates for solid-state quantum optical technologies. Electrical excitation
of emitters may pave the way to scalable on-chip devices, and therefore is
highly sought after. However, most wide band gap materials are not amenable to
efficient doping, which in turn poses challenges on efficient electrical
excitation and on-chip integration. Here, we demonstrate for the first time
room temperature electroluminescence from isolated colour centres in hexagonal
boron nitride (hBN). We harness the van der Waals (vdW) structure of
two-dimensional materials, and engineer nanoscale devices comprised of graphene
- hBN - graphene tunnel junctions. Under an applied bias, charge carriers are
injected into hBN, and result in a localised light emission from the hBN colour
centres. Remarkably, our devices operate at room temperature and produce
robust, narrowband emission spanning a wide spectral range - from the visible
to the near infrared. Our work marks an important milestone in van der Waals
materials and their promising attributes for integrated quantum technologies
and on-chip photonic circuits.
