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Deutscher MBE Workshop 2011

Wir danken allen Teilnehmern und Teilnehmerinnen für einen interessanten und stimulierenden Workshop:

05. - 06.10.2011, Jerusalemkirche, Berlin

Deutscher MBE Workshop

Wir setzen das erfolgreiche Format dieser Reihe von Veranstaltungen fort, die zuletzt in Bochum (2009), Zürich (2008) und Jülich (2007) abgehalten wurden.

more information
International workshop on atomic-scale manipulation and spectroscopy (AMS 2011)

The workshop was held on October 13 and 14, 2011, at NTT Atsugi R&D center.

The workshop is organized by NTT, Japan and PDI, Germany.

We thank all participants who made this workshop a real success!

Workshop webpage
Impressum

gesetzlich vorgesehene Pflichtangaben zur Kennzeichnung und rechtliche Hinweise zur Internetpräsenz (2010)

MIR QCLs

The main results of our MIR QCL studies include

  • the impact of the operating field strength on threshold current density [1]. From the comparison of measured lasing spectra and threshold current densities with  calculated gain spectra obtained by a numerical rate-equation approach using the self-consistent solution of the Schrödinger and Poisson equations, we have shown that the amount of leakage current increases with increasing operating field strength.
  • (Ga,In)(As,N)/(Al,Ga)As heterostructures for intersubband emitters [2]. Such heterostructures exhibit a larger conduction band offset than the GaAs/(Al,Ga)As system which is expected to allow for higher operation temperatures. However, intersubband absorption experiments as well as three-band k·p simulations showed the formation of additional mixed states. Theses states and strong electron scattering at N-related defects reduce the population inversion and apparently prevent the respective QCLs from lasing.
  • the formation of electric-field domains in QCSs [3]. On the basis of our model, we were also able to explain current instabilities observed in some QCSs well below the threshold for lasing with the interplay of local field inhomogeneities within each period with the field domains which span the entire structure.
  • the effect of free-carrier absorption on threshold current density [4]. We have quantitatively shown that the increase of the threshold current density with increasing lasing energy is caused by the increase of the free-carrier absorption in the waveguides which has to be treated quantum mechanically and not classically (Drude model).
  • lasing properties of GaAs/(Al,Ga)As QCLs as a function of injector doping density [5]. We showed that, for an optimum carrier concentration, the lasing energy, the output power, the maximum operating temperature, and the threshold current density exhibit extremal values.

1. L. Schrottke, M. Giehler, R. Hey, and H. T. Grahn,
Quantum-cascade lasers operating at low electric field strengths,
AIP Conf. Proc. 893, 1447-1448 (2007).

2. M. Giehler, R. Hey, P. Kleinert, and H. T. Grahn,
Intersubband transitions in dilute (In,Ga)(As,N)/(Al,Ga)As multiple quantum wells and quantum-cascade laser structures analyzed within a three-band k · p model,
Phys. Rev. B 73, 085322, 8 pages (2006).

3. S. L. Lu, L. Schrottke, S. W. Teitsworth, R. Hey, and H. T. Grahn,
Formation of electric-field domains in GaAs/AlxGa1-xAs quantum-cascade laser structures,
Phys. Rev. B 73, 033311, 4 pages (2006).

4. M. Giehler, H. Kostial, R. Hey, and H. T. Grahn,
Effect of free-carrier absorption on the threshold current density of GaAs/(Al,Ga)As quantum-cascade lasers,
J. Appl. Phys. 96, 4755-4761 (2004).

5. M. Giehler, R. Hey, H. Kostial, S. Cronenberg, T. Ohtsuka, L. Schrottke, and H. T. Grahn,
Lasing properties of GaAs/(Al,Ga)As quantum cascade lasers as a function of injector doping density,
Appl. Phys. Lett. 82, 671-673 (2003).

If you do not have access to one of these journals, please contact us and we can send the corresponding pdf file.
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