AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI+EM-ThM

Paper MI+EM-ThM5
Towards Electrical Spin Injection into a Single InAs/GaAs Quantum Dot

Thursday, November 16, 2006, 9:20 am, Room 2006

Session: Spin Injection
Presenter: C.H. Li, Naval Research Laboratory
Authors: C.H. Li, Naval Research Laboratory
G. Kioseoglou, Naval Research Laboratory
A.T. Hanbicki, Naval Research Laboratory
O.M.J. van 't Erve, Philips Research Laboratories Eindhoven
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
We have demonstrated electrical injection of spin-polarized electrons from an Fe Schottky contact into an ensemble of InAs/GaAs self assembled quantum dots (QDs) in a spin-LED.@footnote 1@ We observed a 5% electron spin polarization from 80-300K, consistent with the suppression of DP spin scattering expected for QDs. The electroluminescence we observed is a convolution of emission from an ensemble of dots with a considerable variation in size, hence it exhibits a broad FWHM of ~50 meV. It is highly desirable to isolate emission from a single QD to further elucidate the details of electrical spin injection and consequent spin polarization in quantum dots as a function of dot size and charge state. To this end, we have developed MBE growth methods to reduce the density of dots by more than an order of magnitude (in the order of 10@super 9@/cm@super 2@ as shown by atomic force microscopy of uncapped samples), and narrowed the aperture sizes of the surface-emitting LEDs to the order of a hundred nanometers using ebeam lithography. As the density and aperture size decrease, the initially broad emission spectrum of the dot ensemble breaks into distinct narrow features attributed to single dot emission. Emission spectra exhibiting a few well-separated peaks are observed with linewidths that are spectrometer resolution-limited. With increasing bias, the number of peaks increases drastically, indicating emission from an increasing number of dots, while the linewidth of these narrow emission peaks broadens, suggesting contributions from various charge states of the dot. Progress towards electrical spin injection into a single QD, and details of the electroluminescence spectra from these single-dot spin-LEDs as a function of bias and magnetic field will be discussed at the meeting. Supported by ONR and DARPA. @FootnoteText@ @footnote 1@C. H. Li et al. APL 86, 132503 (2005).