  Atomic defects in solids offer a versatile basis to study and realize quantum
phenomena and information science in various integrated systems. All-electrical
pumping of single defects to create quantum light emission has been realized in
several platforms including color centers in diamond, silicon carbide, and zinc
oxide, which could lead to the circuit network of electrically triggered
single-photon sources. However, a wide conduction channel which reduces the
carrier injection per defect site has been a major obstacle. Here, we conceive
and realize a novel device concept to construct electrically pumped
single-photon sources using a van der Waals stacked structure with atomic plane
precision. Defect-induced tunneling currents across graphene and NbSe2
electrodes sandwiching an atomically thin h-BN layer allows persistent and
repeatable generation of non-classical light from h-BN. The collected emission
photon energies range between 1.4 and 2.9 eV, revealing the electrical
excitation of a variety of atomic defects. By analyzing the dipole axis of
observed emitters, we further confirm that emitters are crystallographic defect
complexes of h-BN crystal. Our work facilitates implementing efficient and
miniaturized single-photon devices in van der Waals platforms toward
applications in quantum optoelectronics.
