C2v and D3h symmetric InAs quantum dots on GaAs (001) substrate: Exciton emission and a defect field influence

Xiangjun Shang,Xiaowu He,Shulun Li,Zesheng Chen,Zhichuan Niu,Yao Chen,Ben Ma,Haiqiao Ni,Xingliang Su,Yujun Shi

doi:10.1063/5.0019041

Abstract

InAs/GaAs quantum dots (QDs) grown on a GaAs (001) substrate were studied by photoluminescence spectroscopy. Both C2v and D3h QDs with featured XX11, X11+, and XX21+ spectra have been found. A local defect field tunes the dominant exciton from X+ to X or X−, enhances the population on XX, XXX, and XXX−, and induces tunneling and spectral diffusion. In D3h QDs, it also induces a prior e1–h2 transition and a structural polarization of XX21+ and XX11 to build a direct cascade XX21+ − X+. Both XX21+ − X+ and XX − X have no fine structure splitting, promising for entangled photon pair emission. A dominant X+ with slow electron capture (due to background holes) proves a pure single-photon emission.

Highlights

Single InAs quantum dots (QDs) with exciton emission at 900 nm–930 nm were grown on semi-insulating GaAs (001) substrates by solidsource molecular beam epitaxy25,26 and embedded in 1λ-GaAs sandwiched between the top four pairs and the bottom 24 pairs of λ/4GaAs/AlAs distributed Bragg reflectors, a weak cavity with quality factor ∼60 to enhance photon extraction in a wide spectral range for multi-exciton characterization
A dominant X+ with a high slope 1.5 and a wide saturation region 1 ∼ 10P0 is built by background holes that limit electron capture in the QD for a high single photon purity
XX11 has a linewidth of >200 μeV; XX and X have equal linewidths (∼90 μeV in QD1 ∼ 3 larger than X+ of ∼60 μeV due to fine structure splitting (FSS) ∼ 30 μeV); XX2+ and XX3+ have a linewidth of ∼80 μeV, intensity ratio of ∼2, and various spacing

Summary

Introduction

Single InAs QDs with exciton emission at 900 nm–930 nm were grown on semi-insulating GaAs (001) substrates by solidsource molecular beam epitaxy25,26 and embedded in 1λ-GaAs sandwiched between the top four pairs and the bottom 24 pairs of λ/4GaAs/AlAs distributed Bragg reflectors, a weak cavity with quality factor ∼60 to enhance photon extraction in a wide spectral range for multi-exciton characterization.

Results

Conclusion