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Electrical Spin Injection into InGaAs Quantum Dots

  • G. KioseoglouEmail author
  • C. H. Li
  • B. T. Jonker
Reference work entry

Abstract

The electrical injection of spin-polarized electrons from ferromagnetic Fe contacts into self-assembled InGaAs quantum dots (QDs) incorporated in GaAs/AlGaAs spin light-emitting diode (spin-LED) structures is summarized here. The emissions from the ensemble QDs are efficient and broad in energy due to inhomogeneous broadening (QD size distribution). The circular polarization was measured as functions of current, magnetic field, and temperature. Electrical spin injection at room temperature was achieved, and the spin polarization of the QD emission was found to be remarkably insensitive to temperature. Robust spin polarization was also found in the emission from the InAs wetting layer (WL). At low temperatures, a sharp drop in QD polarization at fields around 5 T is observed, attributed to an efficient magnetic field-induced spin relaxation mechanism involving a two-step process when the dots are occupied by three electron–hole pairs. A modified growth method was also employed to produce low-density and high-uniformity dots to study the spin population of individual shell states. Sequential filling of the s-, p-, d-, and f-shells and the control of their polarization were demonstrated using a spin-polarized current from the Fe contact, and the s-p and p-d intershell exchange energies were determined. These results demonstrate that the spin polarization in InGaAs QDs is robust and can be controlled by a spin-polarized electrical current, an important step toward utilizing QDs in next-generation devices for information processing.

Keywords

Quantum Well Circular Polarization Orbit Interaction Spin Lifetime Electrical Injection 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of Abbreviations

2DEG

2-dimensional electron gas

DP

D’yakonov–Perel’

EL

Electroluminescence

FWHM

Full width at half max

HO

Harmonic oscillator

LCP

Left circularly polarized

LED

Light-emitting diode

MBE

Molecular beam epitaxy

ML

Monolayer

PL

Photoluminescence

QD

Quantum dot

QW

Quantum well

RCP

Right circularly polarized

SQUID

Superconducting quantum interference device

TEM

Transmission electron microscopy

WL

Wetting layer

τr

Carrier recombination lifetime

τs

Spin lifetime

Notes

Acknowledgments

The authors gratefully acknowledge the support from core basic research programs at the Naval Research Laboratory and the Office of Naval Research. They also wish to acknowledge the group of Prof. A. Petrou at the State University of New York at Buffalo, and M. Korkusinski and P. Hawrylak at the Quantum Theory Group, National Research Council of Canada, who have contributed significantly to the work presented here.

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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  1. 1.Naval Research LaboratoryWashingtonUSA
  2. 2.Department of Materials Science and TechnologyUniversity of CreteHeraklion CreteGreece

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