Tunneling-Injection Single-Photon Emitter Using Charged Exciton State

Abstract

Practical single-photon emitters (SPEs) using quantum dots (QDs) require high quantum efficiency in order to achieve high-rate and long-distance quantum communication. The strong Coulomb interactions between the carriers in QDs result in the dark-neutral and charged exciton states having distinct energies with bright-neutral excitons. High quantum efficiency can be achieved by suppressing the exclusive processes of the dark and charged excitons such as bright-neutral exciton recombination. However, the selective generation of bright-neutral or charged excitons has not been demonstrated for electrically pumped SPEs. We designed a p–i–n diode structure for constructing an SPE with very high quantum efficiency. This structure enables resonant-tunneling injection of electrons from a quantum well into a QD with two holes. Two holes are induced by controlling a p-doped layer in the vicinity of the QD and the bias voltage. Electrons are injected into the QD one by one using the Coulomb blockade effect. This carrier injection efficiently forms positively charged excitons. In this positively charged exciton state, a single photon is generated each time an electron is injected. Calculation of the electronic structure and Coulomb energies showed that our structure enables high-rate, single-electron injection and subsequent highly efficient single-photon generation in the telecommunication band.