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
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 In0.5Ga0.5As 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.
PACS: 78.67.Hc – Quantum dots / 71.55.Eq – III-V semiconductors
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002