Vanishing biexciton binding energy from stacked, MOVPE grown, site-controlled pyramidal quantum dots for twin photon generation

•Stacked/coupled site-controlled dots deliver statistical distribution of biexciton binding energy.•Molecular like structures with nearly “zero” binding energy tested by photon correlation spectroscopy for the first time.•Proof of concepts of generation of nearly identical twin photons demonstrated with MOVPE grown Pyramidal quantum dots. We characterized stacked double-pyramidal quantum dots which showed biexciton binding energies close to zero by means of photoluminescence and cross-correlation measurements. It was possible to obtain a sequence of two photons with (nearly) the same energy from the biexciton-exciton-ground state cascade, as corroborated by a basic rate-equation model. This type of two-photon emission is both of relevance for fundamental quantum information theory studies as well as for more exotic applicative fields such as quantum biology.