A Semiconductor Exciton Memory Cell Based on a Single Quantum Nanostructure

We demonstrate storage of excitons in a single nanostructure, a self-assembled quantum post. After generation, electrons and holes forming the excitons are separated by an electric field toward opposite ends of the quantum post inhibiting their radiative recombination. After a defined time, the spatially indirect excitons are reconverted to optically active direct excitons by switching the electric field. The emitted light of the stored exciton is detected in the limit of a single nanostructure and storage times exceeding 30 msec are demonstrated. We identify a slow tunneling of the electron out of the quantum post as the dominant loss mechanism by comparing the field dependent temporal decay of the storage signal to models for this process and radiative losses.