  Due to their unique two-dimensional nature, charge carriers in semiconducting
transition metal dichalcogenides (TMDs) exhibit strong unscreened Coulomb
interactions and sensitivity to defects and impurities. The versatility of van
der Waals layer stacking allows spatially separating electrons and holes
between different TMD layers with staggered band structure, yielding interlayer
few-body excitonic complexes whose nature is still debated. Here we combine
quantum Monte Carlo calculations with spectrally and temporally resolved
photoluminescence measurements on a top- and bottom-gated MoSe2/WSe2
heterostructure, and identify the emitters as impurity-bound interlayer
excitonic complexes. Using independent electrostatic control of doping and
out-of-plane electric field, we demonstrate control of the relative populations
of neutral and charged complexes, their emission energies on a scale larger
than their linewidth, and an increase of their lifetime into the microsecond
regime. This work unveils new physics of confined carriers and is key to the
development of novel optoelectronics applications.
