Publication detail

Near-field optical measurement of carrier recombination in InAs/GaAs quantum dots

TOMÁNEK, P., DOBIS, P., BENEŠOVÁ, M., GRMELA, L.

Original Title

Near-field optical measurement of carrier recombination in InAs/GaAs quantum dots

Type

abstract

Language

English

Original Abstract

The applicability of scanning near-field scanning optical microscopy (SNOM) for optical characterization of semiconductors with InAs/GaAs quantum dots is discussed. Highly uniform and sharply aligned InAs QDs were grown on metastable In-GaAs/GaAs structures with cross-hatched dislocation patterns induced by thermal annealing. Photoexcited carrier dynamics are studied using time-resolved photoluminescence in the optical near-field. Comparison with randomly distributed InAs quantum dots grown on planar substrates shows that different channels are responsible for recombination of free carriers. In the case of aligned QDs, the PL intensity increases superlinearly with excitation power, a clear indication of the importance of non-radiative recombination. The carrier dynamics can be described by a set of rate equations that model the capture of holes and electrons from inside the QDs to the dislocation-related traps and to the point traps close to the quantum dots. Numerical calculations show excellent agreement with the experimental results for all excitation powers. Then changing the barrier of sample from 5 nm to the 10 nm, only the capture rate for the dislocation related traps changes due to the larger distance between dots and dislocations. For the sample with 20 nm barrier, a higher concentration of traps near the dots is needed to explain the short carrier lifetimes in the dots for this sample. It should be noted that when simulations were performed with just one type of trap, independently of its parameters, no good fit to the experiment could be obtained. The correlation of experimental data and calculation leads us to presume that several of the standard optical characterization methods can be coupled with SNOM to provide higher spatial resolution in the local measurements. The applicability of SNOM as a real-time in-situ probe shares some of the problems of other proximal probe methods, but offers enough new capabilities to warrant its application.

Keywords

quantum dot, near-field optics, local spectroscopy, carrier recombination

Authors

TOMÁNEK, P., DOBIS, P., BENEŠOVÁ, M., GRMELA, L.

Released

23. 6. 2004

Publisher

Vutium, Brno

Location

Brno

ISBN

80-214-26732-X

Book

Material structure & micromechanics of fracture

Pages from

115

Pages to

115

Pages count

1

BibTex

@misc{BUT59955,
  author="Pavel {Tománek} and Pavel {Dobis} and Markéta {Benešová} and Lubomír {Grmela}",
  title="Near-field optical measurement of carrier recombination in InAs/GaAs quantum dots",
  booktitle="Material structure & micromechanics of fracture",
  year="2004",
  pages="1",
  publisher="Vutium, Brno",
  address="Brno",
  isbn="80-214-26732-X",
  note="abstract"
}