Plenarvorträge - DPG-Tagungen

Halbleiterphysik Montag
basierend auf Streumatrixmethoden[2] verglichen.
[1] A. Christ et al., Phys. Rev. Lett. 91, 183901 (2003)
[2] Chapter 1 in K. Busch et al., Photonic Crystals – Advances in Design,
Fabrication, and Characterization, Wiley VCH (2004)
HL 8.5 Mo 16:15 H15
Focussing Effects in 2D Photonic Crystals — •Frank Hagmann
1 , Kurt Busch 1,2 , and Peter Wölfle 1 — 1 Institut für Theorie
der Kondensierten Materie, Universität Karlsruhe — 2 School of Optics/CREOL
and Department of Physics/University of Central Florida,
Orlando, U.S.A.
HL 9 Heterostrukturen I
Using the multiple multipole method [1] we analyze the optical properties
of finite-sized two-dimensional Photonic Crystal waveguiding structures.
In particular, we study the beaming and focussing abilitites of
various types of straight waveguides and the connection of these effects
to surfaces modes. We show how different surface terminations as
well as surface impedance variations of waveguides allow one to obtain
control over the focussing properties. These enhanced beaming properties
will aid in the design and development of future Photonic Crystal
based devices and of optical interconnects between Photonic Crystal
functional elements and standard index guiding optical components.
[1] A.A.Asatryan, K.Busch, R.C.McPhedran, L.C.Botton, C.M.de Sterke
and N.A.Nicorovici, Waves in Random Media 13,9(2003)
Zeit: Montag 15:15–16:30 Raum: H17
HL 9.1 Mo 15:15 H17
Sputter depth profiling of GaN/InAlGaN multi quantum well
structures — •Gernot Ecke 1 , Rastislav Kosiba 1 , Gabriel Kittler
1 , Nikos Pelekanos 2 , and Oliver Ambacher 1 — 1 Center of
Micro- and Nanotechnologies, TU Ilmenau, D-98693 Ilmenau, Germany
— 2 Foundation for Research and Technology - Hellas, P.O. Box 1527,
GR 71110 Heraklion, Crete, Greece
Multi quantum well (MQW) structures play a crucial role in the design
of many optoelectronic devices. The regularity of these structures,
the composition of the layers, and the quality of the interfaces between
the layers are very important for the device functionality. In this contribution,
the sputter depth profiles across the MQW consisting of seven
GaN/InAlGaN layer pairs with thickness of 7 nm will be presented. The
sputter depth profiling was carried out by Auger electron spectroscopy
in conjunction with argon ion sputtering. Grazing incidence and low ion
energy provided good sputtering conditions for highly depth resolved
measurements. For the evaluation of the depth profiles the factor analysis
of the nitrogen KLL and overlapping Al LMM and Ga MNN Auger
transitions was applied. The deterioration of the true depth profile due
to the sputtering itself as well as due to the information depth of the
Auger electrons was followed by the dynamic Monte Carlo simulation
code TRIDYN. From the good agreement between the measurement and
the simulation the regularity of the measured MQW structure as well as
good interface quality could be proven.
HL 9.2 Mo 15:30 H17
Time-domain THz spectroscopy of electronic exitations in
GaAs/AlGaAs superlattices — •André Dreyhaupt, Stephan
Winnerl, Thomas Dekorsy, and Manfred Helm — Institut
für Ionenstrahlphysik und Materialforschung, Forschungszentrum
Rossendorf, Postfach 51 01 19, 01314 Dresden
We investigate the electronic properties of weakly and more strongly
coupled n-doped GaAs/AlGaAs superlattices by time-domain THz spectroscopy
in the low frequency range from about 0.5 to 3.5 THz. The
sample properties are modulated either by applying an AC voltage via a
gate electrode or by injecting a vertical current. The transmission signal
is detected at the frequency of the modulation voltage with a lock-in amplifier
leading to a signal-to-noise ratio superior compared to conventional
FTIR spectroscopy in this frequency range. We will discuss the observation
of inter-miniband transitions, confined donor transitions, plasmon
excitations and the measurement of intra-miniband THz conductivity in
a wide range of lattice temperatures.
HL 9.3 Mo 15:45 H17
Dynamics of Excitons in Coupled Quantum Well Structures —
•Andreas Gärtner 1 , D. Schuh 2 , and J. P. Kotthaus 1 — 1 CeNS
und Sektion Physik der LMU, München — 2 Walter Schottky Institut,
TU München
The experiments to learn more about motion and interaction of longliving
excitons in coupled quantum wells (QW) [1] are carried out in
semiconductor heterostructures at low temperatures (4 K). These epitaxially
grown samples contain two GaAs-QWs which are separated by
a thin tunnelling barrier.
Metallic gates applied to a sample generate an electrical field perpendicular
to the QW layers. This causes the transition from direct to
spatially indirect excitons, i.e. electron and hole are located in different
QWs. Thus, the overlap of their wave functions is reduced and the exci-
tonic life time increases.
By means of the quantum confined stark effect (QCSE) the vertical electric
field affects the effective excitonic potential [2]. It can be modulated
by interdigitated gate structures [3] leading to in-plane dift phenomena.
In our experimental pump-and-probe-setup we observed these effects
on photo generated excitons by analyzing their emitted photoluminescence
spatially, temporally and spectrally. An intensified CCD-Camera
featuring a temporal resolution in the sub-nanosecond regime allows further
detailed studies on the dynamics of excitonic drift.
[1] Butov et al., Nature 417, 47 (2002)
[2] S. Zimmermann et al., Phys. Rev. B 56, 13414 (1997)
[3] J. Krauß et al., Phys. Rev. Lett. 88, 036803 (2002)
HL 9.4 Mo 16:00 H17
Piezo-electric fields in InGaAsP induced by spontaneous selfordering
— •S. Krämer 1 , G. H. Döhler 1 , S. Neumann 2 , W.
Prost 2 , and T. J. Tegude 2 — 1 Institut für Technische Physik I,
Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, D-91058 Erlangen
— 2 Fachbereich Halbleitertechnik/Halbleitertechnologie, Universität
Duisburg, Lotharstr. 55 LT, D-47048 Duisburg
InGaAsP grown by MOCVD under specific growth conditions form
a monolayer superlattice along the [111] B direction (”spontaneous selfordering”).
This superlattice can be formed by InP-GaAs or InAs-GaP.
Because of the different bond lengths in these combinations the resulting
two ”versions” of InGaAsP would have varying distances between
the alternating layers compared to unstrained bulk material. For In-
GaAsP, grown lattice matched on an InP-substrate, these different layer
sequences lead to significant piezo-electric fields in the range of about 100
kV/cm. The existence of order-induced piezo-electric fields for ordered
GaInP, lattice matched to GaAs, has been discussed controversially in
the literature [1], [2], [3]. To investigate the occurrence, sign, and magnitude
of piezo-electric fields in the InGaAsP-system, we embedded an
InGaAsP - quantum well in an InP - pin and - nip structure, respectively.
By observing the quantum confined Stark effect in the photocurrent signal
in both structures we were able to determine the strength (and sign)
of the piezo-electric field to about 130 kV/cm in ordering direction.
[1]: S. Froyen et al. APL 68, 2852 (1996)
[2]: P. Ernst et al. ICPS 23 World Scientific 1996
[3]: J. D. Perkins et al. JAP, 84 (1998)
HL 9.5 Mo 16:15 H17
Distribution of C-acceptors in delta-doped GaAs studied with
Cross-sectional Scanning Tunneling Microscopy — •L. Winking
1 , M. Wenderoth 1 , T.C.G. Reusch 1 , R.G. Ulbrich 1 , P.-J.
Wilbrandt 2 , R. Kirchheim 2 , S. Malzer 3 , and G. Döhler 3 — 1 IV.
Phys. Inst., Universität Göttingen, Tammannstr.1, D-37077 Göttingen —
2 Inst. f. Materialphysik, Universität Göttingen, Tammannstr.1, D-37077
Göttingen — 3 Inst. f. Techn. Physik I, Universität Erlangen-Nürnberg,
Erwin-Rommel-Str. 1, D-91058 Erlangen
We present XSTM investigations of the C-acceptor-distribution in
delta-doped GaAs. At the intended positions of the C-delta-layers we
found at area-densities of 3×10 12 cm −2 up to extremely high area-densities
of 1 × 10 14 cm −2 a monolayer-sharp spatial distribution of C-acceptors in
growth direction. The slight broadening of less than 0.85nm is found to
be almost symmetric around the intended position of the delta-layer up
to the highest concentration investigated. These results point out that
even at the elevated growth temperature of 570 ◦ C and a very high dopant