Optical imaging of resonant electrical carrier injection into individual quantum dots

TL;DR

This paper demonstrates optical imaging of resonant electrical carrier injection into individual quantum dots, revealing discrete emission and Coulomb interaction effects through micro-electroluminescence spectra.

Contribution

It introduces a method to optically detect resonant carrier injection into single quantum dots via micro-EL imaging, highlighting spatial and spectral features.

Findings

Resonant tunneling causes sharp EL lines from individual QDs.

Surface EL emission fragments into small, discrete light spots.

Coulomb interactions influence selective excitation of QDs.

Abstract

We image the micro-electroluminescence (EL) spectra of self-assembled InAs quantum dots (QDs) embedded in the intrinsic region of a GaAs p-i-n diode and demonstrate optical detection of resonant carrier injection into a single QD. Resonant tunneling of electrons and holes into the QDs at bias voltages below the flat-band condition leads to sharp EL lines characteristic of individual QDs, accompanied by a spatial fragmentation of the surface EL emission into small and discrete light- emitting areas, each with its own spectral fingerprint and Stark shift. We explain this behavior in terms of Coulomb interaction effects and the selective excitation of a small number of QDs within the ensemble due to preferential resonant tunneling paths for carriers.