Eur. Phys. J. B 28, 157-161 (2002)
https://doi.org/10.1140/epjb/e2002-00217-7

Competition in the carrier capture between InGaAs/AlGaAs quantum dots and deep point defects

¹ INFM and Dip. Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy
² CNR-IMEM, Parco delle Scienze 37A, 43010 Fontanini, Parma, Italy

Corresponding author: ^a stefano.sanguinetti@unimib.it

Received: 13 November 2001
Revised: 28 May 2002
Published online: 19 July 2002

Abstract

The presence of an extrinsic photoluminescence (PL) band peaked at 1.356 eV at low temperature is observed, on a large number of self-assembled InAs and In_0.5Ga_0.5As quantum dot (QD) structures, when exciting just below the GaAs absorption edge. A detailed optical characterization allows us to attribute the 1.356 eV PL band to the radiative transition between the conduction band and the doubly ionized acceptor in GaAs. A striking common feature is observed in all investigated samples, namely a resonant quenching of the QD-PL when exciting on the excited level of this deep defect. Moreover, the photoluminescence excitation (PLE) spectrum of the 1.356 eV emission turns out to be almost specular to the QD PLE. This correlation between the PL efficiency of the QDs and the Cu centers evidences a competition in the carrier capture arising from a resonant coupling between the excited level of the defect and the electronic states of the wetting layer on which the QDs nucleate. The estimated Cu concentration is compatible with a contamination during the epitaxial growth.