Light emission and spin-polarised hole injection in InAs/GaAs quantum dot heterostructures with Schottky contact

N. V. Baidus^1,2, M. I. Vasilevskiy^1a, S. V. Khazanova², B. N. Zvonkov², H. P. van der Meulen³, J. M. Calleja³ and L. Viña³

¹ Centro de Física, Universidade do Minho, Campus de Gualtar - Braga 4710-057, Portugal, EU
² Physical-Technical Research Institute, N.I. Lobachevskii University - Nihzniy Novgorod, Russia
³ SEMICUAM, Departamento de Física de Materiales, Universidad Autónoma - Madrid, Spain, EU

^a mikhail@fisica.uminho.pt

Received: 19 November 2011
Accepted: 26 March 2012

Abstract

We demonstrate the feasibility to obtain electroluminescence (EL), up to room temperature, from InGaAs self-assembled quantum dots (QDs) included in a forward-biased Schottky diode. Moreover, using a ferromagnet (FM) as the contact layer, sizable circular polarization of the EL emission in the presence of an external magnetic field is obtained. A resonant behavior of the degree of circular polarization (P) as a function of the applied voltage (V), for a given value of magnetic field, is observed. We explain our findings using a model including tunneling of (spin-polarised) holes through the metal-semiconductor interface, transport in the near-surface region of the heterostructure and out-of-equilibrium statistics of the injected carriers occupying the available states in the QD heterostructure. In particular, the resonant P(V) dependence is related to the splitting of the quasi-Fermi level for two spin orientations in the FM.